add link to rspec_integration example to README
Fix for thread inheritance and diagnostic context.

If another class inherits from the `Thread` class and defines an initializer,
the diagnostic context inheritnace monkey patching will break. It relies on
the fact that the normal Thread `initialize` accepts any number of arguments
and passes them to the block.

refs #56
Merge pull request #55 from charlietanksley/master

Update README to include link to RSpec integration example
Merge pull request #57 from TwP/thread-inheritance-fix

Fix for thread inheritance and diagnostic context.

closes #56
Merge remote-tracking branch 'origin/master' into two-point-oh