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
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