update ruby version

I think vk-ruby must support all 2.1.x versions, so change .ruby-version
Gemfile.lock [is not needed for gem repository](http://stackoverflow.com/questions/4151495/should-gemfile-lock-be-included-in-gitignore)
I think 2.1.4 version enough for travis ci just now ( in most cases 2.1.4 is compatible with other 2.1.x versions)