Add rubocop to gitlab-shell

Gemfile

@@ -7,4 +7,5 @@ group :development, :test do
   gem 'guard'
   gem 'guard-rspec'
   gem 'vcr'
+  gem 'rubocop', '0.28.0', require: false
 end

Gemfile.lock

@@ -2,6 +2,9 @@ GEM
   remote: http://rubygems.org/
   specs:
     addressable (2.3.2)
+    ast (2.0.0)
+    astrolabe (1.3.0)
+      parser (>= 2.2.0.pre.3, < 3.0)
     coderay (1.0.8)
     coveralls (0.7.1)
       multi_json (~> 1.3)
@@ -26,10 +29,14 @@ GEM
     mime-types (2.3)
     multi_json (1.10.1)
     netrc (0.7.7)
+    parser (2.2.0.2)
+      ast (>= 1.1, < 3.0)
+    powerpack (0.0.9)
     pry (0.9.10)
       coderay (~> 1.0.5)
       method_source (~> 0.8)
       slop (~> 3.3.1)
+    rainbow (2.0.0)
     rest-client (1.7.2)
       mime-types (>= 1.16, < 3.0)
       netrc (~> 0.7)
@@ -41,6 +48,13 @@ GEM
     rspec-expectations (2.12.1)
       diff-lcs (~> 1.1.3)
     rspec-mocks (2.12.2)
+    rubocop (0.28.0)
+      astrolabe (~> 1.3)
+      parser (>= 2.2.0.pre.7, < 3.0)
+      powerpack (~> 0.0.6)
+      rainbow (>= 1.99.1, < 3.0)
+      ruby-progressbar (~> 1.4)
+    ruby-progressbar (1.7.1)
     simplecov (0.9.1)
       docile (~> 1.1.0)
       multi_json (~> 1.0)
@@ -64,5 +78,6 @@ DEPENDENCIES
   guard
   guard-rspec
   rspec
+  rubocop (= 0.28.0)
   vcr
   webmock