Reuse code from flashproxy.

Windows don't like slashes in the end of directory names.

- Update README.
- Reset .gitignore.
- Fix documentation.
- Rename EnvException to EnvError.

* Make better use of exceptions instead of relying on retvals.
* If Tor asks us for a transport we don't support, we now send back an
  {S,C}METHOD-ERROR.

pyptlib users shouldn't import pyptlib.easy; they should simply import pyptlib.

This commit only moves code, it does not modify anything.

Now init() returns a dictionary that contains information like the
ORPort, the ExtendedORPort, the state location, etc.