Rename RMagick.rb to rmagick_internal.rb
Fixed: lib/RMagick.rb is overwritten by lib/rmagick.rb on case-insensitive systems
Merge pull request #124 from u338steven/patch-18

Fixed #122: lib/RMagick.rb is overwritten by lib/rmagick.rb on case-insensitive systems
Merge branch 'master' of git://github.com/gemhome/rmagick