Ensure ==/to_s work correctly when raw bytes are passed in different encodings

ensure they are forced to ASCII-8BIT(binary) encoding so ==/to_s doesn't return strings that are encoded differently

I've made allowances for rubies that don't support the force_encoding method (1.8)

-- 

Initially the added test failed with:
```
   test_equality_with_encoding(UUIDTest) 
   <<UUID#70359646839260 time: 2012-12-03 13:47:33 +0000, usecs: 239799 jitter: 9729388734179185554>> expected but was
   <<UUID#70359646839060 time: 2012-12-03 13:47:33 +0000, usecs: 239799 jitter: 9729388734179185554>>.