Update to Chef 11.12.2

Remediates the recently published OpenSSL Heartbleed vulnerability.

http://www.getchef.com/blog/2014/04/08/release-chef-client-11-12-0-10-32-2/
http://www.getchef.com/blog/2014/04/09/release-chef-client-11-12-2/
Pin mailcatcher to latest version

Upstream was broken due to https://github.com/andruby/mailcatcher/pull/6