Stem version parser matches git hash too

Stem's version parser considers the (git-hash) from tor --version output as a part of the version.

Ex: (git-65420e4cb5edcd02) in Tor version 0.2.3.10-alpha-dev (git-65420e4cb5edcd02).

I have fixed this and added a test for get_system_tor_version.

I also made the regex stricter by having it reject version strings whose status_tags have a space in them and properly matching the dot between version integers (. instead of .).

My branch with these fixes -- http://repo.or.cz/w/stem/neena.git/shortlog/refs/heads/fix-version-parsing

Right now, this breaks a few other things. Primarily because GETINFO version returns this:

250-version=0.2.3.10-alpha-dev (git-65420e4cb5edcd02)

One way to fix this would be to stop at the first space in runner.get_tor_version too. I'm going to do that unless someone suggests something better.