use shoulda-matchers instead of shoulda gem

Gemfile

@@ -65,6 +65,6 @@ end
 group :test do
   gem "turn", :require => false
   gem "simplecov", :require => false
-  gem "shoulda", "3.0.1"
+  gem "shoulda-matchers"
   gem 'email_spec'
 end

Gemfile.lock

@@ -269,10 +269,6 @@ GEM
       libwebsocket (~> 0.1.3)
       multi_json (~> 1.0)
       rubyzip
-    shoulda (3.0.1)
-      shoulda-context (~> 1.0.0)
-      shoulda-matchers (~> 1.0.0)
-    shoulda-context (1.0.0)
     shoulda-matchers (1.0.0)
     simplecov (0.6.4)
       multi_json (~> 1.0)
@@ -368,7 +364,7 @@ DEPENDENCIES
   rspec-rails
   sass-rails (= 3.2.3)
   seed-fu
-  shoulda (= 3.0.1)
+  shoulda-matchers
   simplecov
   six
   sqlite3