Fix Rubocop offenses

Author: tmilewski

Gemfile

@@ -3,6 +3,7 @@ source "http://rubygems.org"
 gem "rake", "~> 10.5"
 
 group :test do
+  gem "addressable", "~> 2.3.8", :platforms => %i[jruby ruby_18]
   gem "coveralls"
   gem "json", :platforms => %i[jruby ruby_18 ruby_19]
   gem "mime-types", "~> 1.25", :platforms => %i[jruby ruby_18]
@@ -12,7 +13,6 @@ group :test do
   gem "rubocop", ">= 0.51", :platforms => %i[ruby_19 ruby_20 ruby_21 ruby_22 ruby_23 ruby_24]
   gem "simplecov", ">= 0.9"
   gem "webmock", "~> 1.0"
-  gem "addressable", "~> 2.3.8", :platforms => [:jruby, :ruby_18]
 end
 
 # Specify your gem's dependencies in omniauth-oauth2.gemspec