Squashing asset pipeline bugs and other stuff

1. Update dependencies
   - Add font-awesome as dependency
   - Switch to Bootstrap 4 dev branch
   - Remove eslint airbnb style (we're not using it)

2. Imported images and fonts should go into dist/images
   and dist/fonts, respectively

3. Only lint our own code, not external code (fixes #1633)

assets/scripts/main.js

@@ -1,12 +1,13 @@
-import $ from 'jquery';
+// import external dependencies
+import 'jquery'
+import 'bootstrap/dist/js/bootstrap'
+
+// import local dependencies
 import Router from './util/router';
 import common from './routes/Common';
 import home from './routes/Home';
 import about_us from './routes/About';
 
-// Import npm dependencies
-import 'bootstrap/dist/js/bootstrap';
-
 // Use this variable to set up the common and page specific functions. If you
 // rename this variable, you will also need to rename the namespace below.
 const routes = {

assets/styles/common/_variables.scss

@@ -5,3 +5,6 @@ $sidebar-sm-columns:    4;
 
 // Colors
 $brand-primary:         #27ae60;
+
+// Font Awesome | see: http://fontawesome.io/get-started/
+$fa-font-path:          '~font-awesome/fonts';

assets/styles/main.scss

@@ -2,6 +2,7 @@
 
 // Import npm dependencies
 @import "~bootstrap/scss/bootstrap";
+@import "~font-awesome/scss/font-awesome";
 
 @import "common/global";
 @import "components/buttons";