python support absolute file path

#4 implemented python support, but only for files in the current directory. It would be nice to expand this support to handle all files (if they are within the current project), such as:

`File "/home/josh/workspace/pyrs/pyrs/transpiler.py", line 34, in trans`

Given I am working in the `/home/josh/workspace/pyrs` directory, this should resolve to filename `pyrs/transpiler.py`.