Fix failing tests

FIXED: MockHTTPService no longer does string comparison; it now decodes and compares Ruby objects.
FIXED: Other failing tests are now fixed.

After building up several layers of elaborate JSON encoding and parsing hacks to deal with string comparison problems in the mocked Facebook tests, I've finally ripped all that out and now compare Ruby objects with each other.  Infinitely more flexible and happy and compatible. 

I've also fixed some other test failures, which seem to have arisen because stubbing Proc#call (or maybe it's #call on a block) doesn't seem to work properly with some Rubies.  That's now tested another way.