When running the curl, first errors are:

Cloning MagicMirror ...
Cloning into 'MagicMirror'...
remote: Counting objects: 6447, done.
remote: Compressing objects: 100% (14/14), done.
remote: Total 6447 (delta 4), reused 0 (delta 0), pack-reused 6433
Receiving objects: 100% (6447/6447), 10.82 MiB | 404.00 KiB/s, done.
Resolving deltas: 100% (3515/3515), done.
Checking connectivity... done.
Cloning MagicMirror Done!
Installing dependencies ...
npm WARN prefer global coffee-script@1.10.0 should be installed with -g
npm WARN prefer global jsonlint@1.6.2 should be installed with -g
npm WARN prefer global colorguard@1.2.0 should be installed with -g

> electron@1.6.2 postinstall /home/pi/MagicMirror/node_modules/electron
> node install.js
Unable to install dependencies!

Then I ran npm start to see what would happen:

pi@raspberrypi:~/MagicMirror $ npm start

> magicmirror@2.1.0 start /home/pi/MagicMirror
> electron js/electron.js

/home/pi/MagicMirror/node_modules/electron/index.js:9
  throw new Error('Electron failed to install correctly, please delete node_modules/' + path.basename(__dirname) + ' and try installing again')
  ^

Error: Electron failed to install correctly, please delete node_modules/electron and try installing again
    at Object. (/home/pi/MagicMirror/node_modules/electron/index.js:9:9)
    at Module._compile (module.js:570:32)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.require (module.js:497:17)
    at require (internal/module.js:20:19)
    at Object. (/home/pi/MagicMirror/node_modules/electron/cli.js:3:16)
    at Module._compile (module.js:570:32)

npm ERR! Linux 4.9.13-v7+
npm ERR! argv "/usr/bin/nodejs" "/usr/bin/npm" "start"
npm ERR! node v6.10.0
npm ERR! npm  v3.10.10
npm ERR! code ELIFECYCLE
npm ERR! magicmirror@2.1.0 start: `electron js/electron.js`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the magicmirror@2.1.0 start script 'electron js/electron.js'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the magicmirror package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     electron js/electron.js
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs magicmirror
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls magicmirror
npm ERR! There is likely additional logging output above.

npm ERR! Please include the following file with any support request:
npm ERR!     /home/pi/MagicMirror/npm-debug.log

So, I can delete node_modules, but how would I go about reinstalling?

Below is the npm debug file

0 info it worked if it ends with ok
1 verbose cli [ '/usr/bin/nodejs', '/usr/bin/npm', 'start' ]
2 info using npm@3.10.10
3 info using node@v6.10.0
4 verbose run-script [ 'prestart', 'start', 'poststart' ]
5 info lifecycle magicmirror@2.1.0~prestart: magicmirror@2.1.0
6 silly lifecycle magicmirror@2.1.0~prestart: no script for prestart, continuing
7 info lifecycle magicmirror@2.1.0~start: magicmirror@2.1.0
8 verbose lifecycle magicmirror@2.1.0~start: unsafe-perm in lifecycle true
9 verbose lifecycle magicmirror@2.1.0~start: PATH: /usr/lib/node_modules/npm/bin/node-gyp-bin:/home/pi/MagicMirror/node_modules/.bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games
10 verbose lifecycle magicmirror@2.1.0~start: CWD: /home/pi/MagicMirror
11 silly lifecycle magicmirror@2.1.0~start: Args: [ '-c', 'electron js/electron.js' ]
12 silly lifecycle magicmirror@2.1.0~start: Returned: code: 1  signal: null
13 info lifecycle magicmirror@2.1.0~start: Failed to exec start script
14 verbose stack Error: magicmirror@2.1.0 start: `electron js/electron.js`
14 verbose stack Exit status 1
14 verbose stack     at EventEmitter. (/usr/lib/node_modules/npm/lib/utils/lifecycle.js:255:16)
14 verbose stack     at emitTwo (events.js:106:13)
14 verbose stack     at EventEmitter.emit (events.js:191:7)
14 verbose stack     at ChildProcess. (/usr/lib/node_modules/npm/lib/utils/spawn.js:40:14)
14 verbose stack     at emitTwo (events.js:106:13)
14 verbose stack     at ChildProcess.emit (events.js:191:7)
14 verbose stack     at maybeClose (internal/child_process.js:877:16)
14 verbose stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:226:5)
15 verbose pkgid magicmirror@2.1.0
16 verbose cwd /home/pi/MagicMirror
17 error Linux 4.9.13-v7+
18 error argv "/usr/bin/nodejs" "/usr/bin/npm" "start"
19 error node v6.10.0
20 error npm  v3.10.10
21 error code ELIFECYCLE
22 error magicmirror@2.1.0 start: `electron js/electron.js`
22 error Exit status 1
23 error Failed at the magicmirror@2.1.0 start script 'electron js/electron.js'.
23 error Make sure you have the latest version of node.js and npm installed.
23 error If you do, this is most likely a problem with the magicmirror package,
23 error not with npm itself.
23 error Tell the author that this fails on your system:
23 error     electron js/electron.js
23 error You can get information on how to open an issue for this project with:
23 error     npm bugs magicmirror
23 error Or if that isn't available, you can get their info via:
23 error     npm owner ls magicmirror
23 error There is likely additional logging output above.
24 verbose exit [ 1, true ]