add therubyracer gem

Gemfile

@@ -11,7 +11,7 @@ gem 'uglifier', '>= 1.3.0'
 # Use CoffeeScript for .coffee assets and views
 gem 'coffee-rails', '~> 4.1.0'
 # See https://github.com/sstephenson/execjs#readme for more supported runtimes
-# gem 'therubyracer', platforms: :ruby
+gem 'therubyracer', platforms: :ruby
 
 # Use jquery as the JavaScript library
 gem 'jquery-rails'

Gemfile.lock

@@ -181,6 +181,7 @@ GEM
     leaflet-markercluster-rails (0.7.0)
       railties (>= 3.1)
     leaflet-rails (0.7.4)
+    libv8 (3.16.14.7)
     listen (3.0.4)
       rb-fsevent (>= 0.9.3)
       rb-inotify (>= 0.9)
@@ -277,6 +278,7 @@ GEM
       ffi (>= 0.5.0)
     rdoc (4.2.0)
       json (~> 1.4)
+    ref (2.0.0)
     request_store (1.1.0)
     responders (2.1.0)
       railties (>= 4.2.0, < 5)
@@ -365,6 +367,9 @@ GEM
       httpclient (>= 2.4)
       i18n
       json (>= 1.4.3)
+    therubyracer (0.12.2)
+      libv8 (~> 3.16.14.0)
+      ref
     thor (0.19.1)
     thread_safe (0.3.5)
     tilt (1.4.1)
@@ -462,6 +467,7 @@ DEPENDENCIES
   simplecov
   spring
   spring-commands-rspec
+  therubyracer
   timecop
   turbolinks
   uglifier (>= 1.3.0)