Fix version.rb require path

During compilation, extconf.rb is located in
tmp/x86_64-linux/RMagick2/$RUBY_VERSION
fix path for build
Merge pull request #142 from mockdeep/path_fix

Fix version require path
Make Travis notify Gitter chat room 'gemhome'
Reroute Travis notifications to rmagick repo chat
Add Gitter badge to README
Put all badges in one line

Unfortunately, there doesn't seem to be a way to do this while keeping
the source code in separate lines :(
move deprecated RMagick.rb file