Replace SASS with assets from Ghost-UI

closes #2368
- Remove Ruby dependency (Gemfiles)
- Remove sass/fonts from core/client/assets/
- Add copy task to Gruntfile to copy over ghost-ui assets
- Install Ghost-UI via bower
- Changed .npmignore/.gitignore
- Remove grunt-contrib-sass dependency
- Remove mentions of Ruby in CONTRIBUTING.md
Merge pull request #2369 from halfdan/bower_all_the_things

Replace SASS with assets from Ghost-UI
Cleanup more sass/ruby things
Bower dependency cleanup

issue #2272

- handlebars version should match node (1.3.0)
- iCheck isn't used
Clean up markdown help modal

* Shorter, more user friendly.
* See #1463 - Not fixing in any way, just related.
Blog post titles will now be properly escaped in rss (xml) feeds (reopens #715)

Closes #2313
Merge pull request #2383 from JohnONolan/clean-markdowntips

Clean up markdown help modal
Merge pull request #2318 from knunery/fix-2313

Blog post titles will now be properly escaped in rss (xml) feeds.
Add promise to ghost startup process to allow
hooking into when ghost has finished loading

addresses item 9 in #2078
and makes progress on #2182

- has files that startup ghost return a promise
 that is resolved once ghost has finished loading
- moves getSocket into config file
- removes models.reset() as it's not used anywhere
- update functions in server startup
- remove unused version hash variable
Adding .bowerrc

If no .bowerrc file is found in the current folder it seems to lookup if one exists in parent folders. Thus, we need to use .bowerrc in order to avoid problems.
Merge pull request #2225 from hswolff/ghost-startup

Add promise to ghost startup process to allow
Merge pull request #2386 from manuelmitasch/add-bowerrc

Adding .bowerrc
Updating ghost-ui
Serve default robots.txt

closes #2062
- Server robots.txt from theme if available
- Serve default robots.txt from /core/shared/ otherwise
- Added tests for default robots.txt