Import stylesheets from style-guide

[hursey013]

This removes the majority of the app's stylesheets, instead importing them from a shared style guide npm package.

I'm using a github branch for the identity-style-guide npm package for testing, but once it all looks good I can bump the version of the package and update this PR to reflect.

[nickbristow]

From a code perspective, it seems fine to me.

[nickbristow]

I'm getting an error trying to run this locally, but i think its unrelated

~/Projects/18f/identity-idp (bh-remove-styles) $ sudo npm install
npm ERR! code 1
npm ERR! Command failed: /usr/local/bin/git clone --depth=1 -q -b bh-add-app-styles git://github.com/18f/identity-style-guide.git /Users/richardbristow/.npm/_cacache/tmp/git-clone-7ddc295b
npm ERR! /Users/richardbristow/.npm/_cacache/tmp/git-clone-7ddc295b/.git: Permission denied
npm ERR! 

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/richardbristow/.npm/_logs/2017-08-17T20_52_01_972Z-debug.log

[gemfarmer]

LGTM!

[zachmargolis]

This is just a redo of the other commit right? LGTM now that the chef build will run the right npm commands

[hursey013]

@zachmargolis the previous PR just imported fonts & favicons - this extends that to now also include stylesheets.

[zachmargolis]

@hursey013 got it, thanks for explaining! Still LGTM!