Bump rake from 11.3.0 to 12.2.1

Bumps [rake](https://github.com/ruby/rake) from 11.3.0 to 12.2.1.
- [Changelog](https://github.com/ruby/rake/blob/master/History.rdoc)
- [Commits](ruby/rake@v11.3.0...v12.2.1)

Gemfile

@@ -53,7 +53,7 @@ gem 'yaml_db'
 
 # http://stackoverflow.com/questions/35893584/nomethoderror-undefined-method-last-comment-after-upgrading-to-rake-11
 # same error in travis build with rake v12.0.0, so I chose to pin rake back
-gem 'rake', '~> 11.3.0'
+gem 'rake', '~> 12.2.1'
 
 # -------------------
 gem 'honeybadger', '~> 3.1'

Gemfile.lock

@@ -324,7 +324,7 @@ GEM
       rake (>= 0.8.7)
       thor (>= 0.18.1, < 2.0)
     rainbow (2.2.1)
-    rake (11.3.0)
+    rake (12.2.1)
     ransack (1.7.0)
       actionpack (>= 3.0)
       activerecord (>= 3.0)
@@ -512,7 +512,7 @@ DEPENDENCIES
   pubmed_search
   rails (~> 4.2.10)
   rails_db
-  rake (~> 11.3.0)
+  rake (~> 12.2.1)
   responders (~> 2.4)
   rest-client
   retina_tag