Add .ruby-version

https://rvm.io/workflow/projects#supported-files
Improve style of modal window on /user/recipe/note
Merge pull request #429 from shinnn/note-style

Improve style of modal window on /user/recipe/note
Remove unnecessary vendor prefixes

Because we use autoprefixer-rails now.
Merge pull request #431 from shinnn/issue-430

fix #430, remove unnecessary vendor prefixes
Merge pull request #419 from shinnn/add-ruby-version

Add .ruby-version file