Add Contributor's Guide
Fix wrong relative path for lib/rmagick/version
Merge pull request #139 from marwan-tanager/master

Fix wrong relative path for lib/rmagick/version
Merge pull request #136 from vassilevsky/contributors-guide

Add Contributor's Guide
Fix version.rb require path

During compilation, extconf.rb is located in
tmp/x86_64-linux/RMagick2/$RUBY_VERSION