Version 0.2.8 - release candidate

* Return public key on /key/:login
* rake tasks clean up expired tokens and sessions (#4568)
* rake task to dump design docs to files
* add dump_design_docs to CouchRest::Model::Utils:Migrate
* rename ticket title to subject

lib/leap_web/version.rb

 module LeapWeb
-  VERSION = "0.2.7" unless defined?(LeapWeb::VERSION)
+  VERSION = "0.2.8.rc" unless defined?(LeapWeb::VERSION)
 end