Upgrade to Ruby 2.0

We're now ready to merge this and run travis against ruby 2.0 and 1.9.3.

Links to related issues:

UTF-8 default encoding of ruby scripts:
#218 
#465 
#589
#715 
#732
#804 

Protected methods don't respond_to?
#685 

File descriptors are closed on exec (when spawning a new process)
#459 
#682

Others:
#233 
#581 

Patches/extensions:
#535 
#536 
#714 
#728 
#826 

There are remaining open ruby 2 issues unrelated to getting ruby 2.0 on travis:
https://github.com/ManageIQ/manageiq/labels/ruby%202
Same here.