Add tracepoint.rb to 2.0.0

Hi, last night I finally reworked my the original TracePoint, library to compatible with Ruby 2.0. new rendition (as I mention in issue #65).

It's not 100%. Unfortunately I don't have the time to put the final polish on, but it is very close, and it is functional. I left a few TODOs in the code about what's left to work out. There isn't much, the primary thing is the proper definitions of `raised_exception` and `return_value`. Those are new, and I am not sure how they are (or if they even can be) defined. HTH.