adding support for lambda functions

- and tests for numpy and math functions

- rounding 2nd arg for math.pow test
  (it does not like negatives raised to non-integers)
Merge remote-tracking branch 'upstream/master' into ast-fixes

- This is a straightforward merge of @bptripp's stuff
- I'm going to go back and make another commit to better
  integrate our work
Got all ast conversion tests passing

- @bptripp's lambda function code is now fully integrated
  with my additions