removed debugger from gemspec; it’s platform-specific

mri 1.9 uses debugger
mri 2.x uses debugger2
rbx uses rubinius-debugger
etc.
Fix for Rubinius

It seems to break when modifying the array it’s
looping over. Besides, this way is cleaner.
Merge branch 'rbx' of https://github.com/emptyflask/carmen into emptyflask-rbx

Conflicts:
	carmen.gemspec