Win support

Here is a working version of support for Windows for #28 
All tests are passing.
Most of the adjustments were on the quirks of MSFT of course, such as command line arguments quoting, no support for Signals, adjusting tests expectations in particular line endings.
This is working acceptably enough in that state, though it may not be bullet proof as it is as there are too many process handling quirks in Windows compared to POSIX.

That said, this could be a great addition for now.
I could then work out integrating something like mozprocess that provides enhanced handling of Windows processes and should make the Windows side more solid.


```
(honcho) c:\w421\honcho>nosetests
............................
----------------------------------------------------------------------
Ran 28 tests in 18.568s

OK
```