Update the expected version of rake

This should ease usage of the Vagrant box, no longer requiring usage of
`bundle exec` during development and tests

Gemfile.lock

@@ -151,7 +151,7 @@ GEM
       rake (>= 0.8.7)
       rdoc (~> 3.4)
       thor (~> 0.14.4)
-    rake (11.2.2)
+    rake (12.0.0)
     rb-readline (0.5.3)
     rdoc (3.10)
       json (~> 1.4)