Add VERSION to auto-loaded constants

[ransombriggs]

Before

irb(main):001:0> $:.unshift 'lib'
irb(main):002:0> require 'super_diff'
=> true
irb(main):003:0> SuperDiff::VERSION
NameError (uninitialized constant SuperDiff::VERSION)

After

irb(main):001:0> $:.unshift 'lib'
irb(main):002:0> require 'super_diff'
=> true
irb(main):003:0> SuperDiff::VERSION
=> "0.8.0"

[ransombriggs]

I merged master can you kick off the test suite again?

[mcmire]

Done and merged!