Add rubocop to development group in gemfile

Gemfile

@@ -129,4 +129,5 @@ group :development do
   gem 'guard-zeus'
   gem 'guard-rspec'
   gem 'parallel_tests'
+  gem 'rubocop'
 end

Gemfile.lock

@@ -165,6 +165,7 @@ GEM
     angularjs-rails (1.5.5)
     ansi (1.4.2)
     arel (3.0.3)
+    ast (2.3.0)
     atomic (1.1.99)
     awesome_nested_set (2.1.5)
       activerecord (>= 3.0.0)
@@ -480,6 +481,8 @@ GEM
     parallel (1.4.1)
     parallel_tests (1.3.7)
       parallel
+    parser (2.4.0.0)
+      ast (~> 2.2)
     paypal-sdk-core (0.2.10)
       multi_json (~> 1.0)
       xml-simple
@@ -494,6 +497,7 @@ GEM
     polyamorous (0.5.0)
       activerecord (~> 3.0)
     polyglot (0.3.5)
+    powerpack (0.1.1)
     pry (0.9.12.2)
       coderay (~> 1.0.5)
       method_source (~> 0.8)
@@ -531,6 +535,8 @@ GEM
       rake (>= 0.8.7)
       rdoc (~> 3.4)
       thor (>= 0.14.6, < 2.0)
+    rainbow (2.2.2)
+      rake
     raindrops (0.13.0)
     rake (11.1.2)
     ransack (0.7.2)
@@ -578,6 +584,12 @@ GEM
       rspec-mocks (~> 2.14.0)
     rspec-retry (0.4.2)
       rspec-core
+    rubocop (0.48.1)
+      parser (>= 2.3.3.1, < 3.0)
+      powerpack (~> 0.1)
+      rainbow (>= 1.99.1, < 3.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (~> 1.0, >= 1.0.1)
     ruby-progressbar (1.7.1)
     rubyzip (1.2.0)
     safe_yaml (0.9.5)
@@ -620,6 +632,7 @@ GEM
     uglifier (2.7.1)
       execjs (>= 0.3.0)
       json (>= 1.8.0)
+    unicode-display_width (1.3.0)
     unicorn (4.9.0)
       kgio (~> 2.6)
       rack
@@ -723,6 +736,7 @@ DEPENDENCIES
   roo (~> 2.7.0)
   rspec-rails
   rspec-retry
+  rubocop
   sass (~> 3.3)
   sass-rails (~> 3.2.3)
   shoulda-matchers
@@ -749,4 +763,4 @@ RUBY VERSION
    ruby 2.1.5p273
 
 BUNDLED WITH
-   1.14.3
+   1.15.1