Fixes#3813
- Add togglePreview action to controller
- Implement action and bind attributes
- Remove the now pointless
- Update to comply with issue suggestions
Closes#3254, closes#3138, closes#3245
### Settings Routing and View refactoring
- Refactored `SettingsView` to handle transitions between mobile and desktop layouts
- `SettingsRoute` will only transition to `settings.general` if the screen is large enough to show both the menu and the content
- Added `SettingsIndexView` to handle showing the settings menu on mobile screens
- Added `SettingsContentBaseView` to be inherited by any settings view that is not index.
- Updated Settings templates appropriately to work with new views
- Removed extraneous `active` class from `settings-content`
- Changed settings menu to use `gh-activating-list-item`
- Retooled settings tests
### Mobile Utils
- Renamed file to `mobile.js`, since it's inside of `utils/`
- Added `mobileQuery` MediaQueryList to help detect layout changes
- Removed unused `hasTouchScreen`, `device.js` should be used instead.
- Removed unused `smallScreen` function
- Moved FastClickInit to codemirror-mobile
closes#2957
- add FastClick library to Gruntfile.js
- add touch-editor to client/assets/lib/
- add mobile-specific utils to util/mobile-utils.js
- add codemirror util to set up TouchEditor only if we're really on mobile
- change gh-codemirror from having a default action to a named action. prevents Ember.TextArea firing action on change
- change gh-codemirror `cm.getDoc().getValue()` to `cm.getValue()` for portability
- change codemirror-shortcuts ES6 export/import style
- changed ghostimagepreview.js to check for Ember.touchEditor in addition to Ghost.touchEditor
