Update system emails to come from ghost@blog.url

Closes #2145
Merge pull request #2345 from JohnONolan/emailfrom

Update system emails to come from ghost@blog.url
Do not cache 404 pages

closes #2334

- remove call to set cache-control in 404 response header
- update unit tests to expect this

Fix up unit tests
Merge pull request #2342 from dsschnau/nocache404

Nocache404
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
Merge branch 'master' into ember

Conflicts:
	.gitignore
	.npmignore
	Gemfile.lock
	Gruntfile.js
	bower.json
	core/clientold/assets/fonts/icons.dev.svg
	core/clientold/assets/fonts/icons.eot
	core/clientold/assets/fonts/icons.svg
	core/clientold/assets/fonts/icons.ttf
	core/clientold/assets/fonts/icons.woff
	core/clientold/assets/sass/ie.scss
	core/clientold/assets/sass/layouts/auth.scss
	core/clientold/assets/sass/layouts/editor.scss
	core/clientold/assets/sass/layouts/errors.scss
	core/clientold/assets/sass/layouts/manage.scss
	core/clientold/assets/sass/layouts/plugins.scss
	core/clientold/assets/sass/layouts/settings.scss
	core/clientold/assets/sass/layouts/users.scss
	core/clientold/assets/sass/modules/animations.scss
	core/clientold/assets/sass/modules/breakpoint.scss
	core/clientold/assets/sass/modules/breakpoint/_context.scss
	core/clientold/assets/sass/modules/breakpoint/_helpers.scss
	core/clientold/assets/sass/modules/breakpoint/_no-query.scss
	core/clientold/assets/sass/modules/breakpoint/_parsers.scss
	core/clientold/assets/sass/modules/breakpoint/_respond-to.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/_double.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/_query.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/_resolution.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/_single.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/_triple.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/double/_default-pair.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/double/_default.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/double/_double-string.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/resolution/_resolution.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/single/_default.scss
	core/clientold/assets/sass/modules/breakpoint/parsers/triple/_default.scss
	core/clientold/assets/sass/modules/forms.scss
	core/clientold/assets/sass/modules/global.scss
	core/clientold/assets/sass/modules/icons.scss
	core/clientold/assets/sass/modules/mixins.scss
	core/clientold/assets/sass/modules/normalize.scss
	core/clientold/assets/sass/screen.scss