Update therubyracer to get rid of memory leak.

Reference: rubyjs/therubyracer#336

Gemfile.lock

@@ -154,7 +154,7 @@ GEM
  actionmailer (>= 3.2)
  letter_opener (~> 1.0)
  railties (>= 3.2)
- libv8 (3.16.14.7)
+ libv8 (3.16.14.13)
  lodash-rails (3.7.0)
  railties (>= 3.1)
  loofah (2.0.1)
@@ -245,7 +245,7 @@ GEM
  rdiscount (2.1.8)
  rdoc (4.2.0)
  json (~> 1.4)
- ref (1.0.5)
+ ref (2.0.0)
  remotipart (1.2.1)
  responders (2.1.0)
  railties (>= 4.2.0, < 5)
@@ -300,7 +300,7 @@ GEM
  actionpack (>= 3.0)
  activesupport (>= 3.0)
  sprockets (>= 2.8, < 4.0)
- therubyracer (0.12.1)
+ therubyracer (0.12.2)
  libv8 (~> 3.16.14.0)
  ref
  thor (0.19.1)
@@ -372,4 +372,4 @@ DEPENDENCIES
  web-console (~> 2.0)
 
 BUNDLED WITH
- 1.10.5
+ 1.11.2