Add RuboCop

Gemfile.lock

@@ -126,6 +126,7 @@ GEM
       capybara (~> 3.13, < 4)
       websocket-driver (>= 0.6.5)
     arel (9.0.0)
+    ast (2.4.2)
     attribute_normalizer (1.2.0)
     base32 (0.3.4)
     better_errors (2.9.1)
@@ -313,6 +314,9 @@ GEM
     nokogiri (1.11.1)
       mini_portile2 (~> 2.5.0)
       racc (~> 1.4)
+    parallel (1.20.1)
+    parser (3.0.0.0)
+      ast (~> 2.4.1)
     pdf-core (0.9.0)
     polyglot (0.3.5)
     prawn (2.4.0)
@@ -404,6 +408,7 @@ GEM
       redis-namespace (~> 1.6)
       sinatra (>= 0.9.2)
       vegas (~> 0.1.2)
+    rexml (3.2.4)
     roo (2.8.3)
       nokogiri (~> 1)
       rubyzip (>= 1.3.0, < 3.0.0)
@@ -434,9 +439,28 @@ GEM
     rspec-rerun (1.1.0)
       rspec (~> 3.0)
     rspec-support (3.10.2)
+    rubocop (1.11.0)
+      parallel (~> 1.10)
+      parser (>= 3.0.0.0)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 1.8, < 3.0)
+      rexml
+      rubocop-ast (>= 1.2.0, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 1.4.0, < 3.0)
+    rubocop-ast (1.4.1)
+      parser (>= 2.7.1.5)
+    rubocop-rails (2.9.1)
+      activesupport (>= 4.2.0)
+      rack (>= 1.1)
+      rubocop (>= 0.90.0, < 2.0)
+    rubocop-rspec (2.2.0)
+      rubocop (~> 1.0)
+      rubocop-ast (>= 1.1.0)
     ruby-filemagic (0.7.2)
     ruby-ole (1.2.12.2)
     ruby-prof (1.4.3)
+    ruby-progressbar (1.11.0)
     ruby-units (2.3.2)
     ruby2_keywords (0.0.4)
     ruby_parser (3.15.1)
@@ -515,6 +539,7 @@ GEM
     unf (0.1.4)
       unf_ext
     unf_ext (0.0.7.7)
+    unicode-display_width (2.0.0)
     uniform_notifier (1.13.2)
     vegas (0.1.11)
       rack (>= 1.0.0)
@@ -605,6 +630,9 @@ DEPENDENCIES
   rspec-core
   rspec-rails
   rspec-rerun
+  rubocop
+  rubocop-rails
+  rubocop-rspec
   ruby-filemagic
   ruby-prof
   ruby-units