Initial implementation if license template selector and /licenses/:key API endpoint

Gemfile

Gemfile.lock

app/assets/javascripts/api.js.coffee

app/assets/javascripts/blob/blob_license_selector.js.coffee

app/assets/stylesheets/pages/editor.scss

app/controllers/projects/blob_controller.rb

app/helpers/projects_helper.rb

app/views/projects/blob/_editor.html.haml

app/views/projects/empty.html.haml

lib/api/api.rb

lib/api/licenses.rb

spec/requests/api/licenses_spec.rb