[PATCH 0 of 1 hglib POC] hglib: a Python wrapper around hg's cmdserver

[Idan Kamara]

- hgclient.commit() is hacky: it uses hgclient.tip() to return the committed revision.
  afaik there's no way to get 'hg commit' to output the just committed node id,
  maybe it needs a new option? (import is also problematic)

- I discovered it's impossible to use '\0' (e.g. in --template),
  due to it being used as the args delimiter in the command protocol runcommand.
  Style files saved the day here, but this is still a limitation of the protocol.

- I used a hybrid of Python's unittest and run-tests.
  I'm not sure if run-tests is really needed here, but for now it made things easier.

- pretty sure I used some Python 2.6/7 stuff in there, what is our minimum Python version for this?
- for now this initial patch is quite big, I'll split it later on