Wrong version number in master and 2015.10.28 release

@manveru the master has the '2012.12.08' release version
https://github.com/Ramaze/ramaze/blob/master/ramaze.gemspec#L3

So does the '2015.10.28' release
https://github.com/Ramaze/ramaze/blob/2015.10.28/lib/ramaze/version.rb#L2

This is  extremely confusing when trying to upgrade or install the gem.
