Fix Rubocop errors (#214)

* Fix for google-style 0.3.0 change to Style/WordArray.
* Update google-style dependency to 0.3.

Gemfile

@@ -8,7 +8,7 @@ group :development do
   gem "coveralls", "~> 0.7"
   gem "fakefs", "~> 0.6"
   gem "fakeredis", "~> 0.5"
-  gem "google-style", "~> 0.2"
+  gem "google-style", "~> 0.3"
   gem "logging", "~> 2.0"
   gem "rack-test", "~> 0.6"
   gem "rake", "~> 10.0"

lib/googleauth/user_refresh.rb

@@ -79,7 +79,7 @@ module Google
       # JSON key.
       def self.read_json_key json_key_io
         json_key = MultiJson.load json_key_io.read
-        wanted = %w[client_id client_secret refresh_token]
+        wanted = ["client_id", "client_secret", "refresh_token"]
         wanted.each do |key|
           raise "the json is missing the #{key} field" unless json_key.key? key
         end