Add rake to Gemfile

Gemfile

@@ -24,3 +24,5 @@ gem "wdm", "~> 0.1.0", :platforms => [:mswin, :mingw]
 platforms :mri_18 do
   gem "ruby18_source_location"
 end
+
+gem "rake", "~> 10.1.0"
\ No newline at end of file

Gemfile.lock

@@ -125,6 +125,7 @@ DEPENDENCIES
   middleman-gh-pages
   middleman-livereload (~> 3.1.0)
   middleman-syntax
+  rake (~> 10.1.0)
   redcarpet!
   ruby18_source_location
   wdm (~> 0.1.0)