run_tests.py fails on Windows

When running run_tests.py on Windows, it will complain that "'module' object has no attribute 'sysconf'". The reason it that os.sysconf, which is used out of a try/except clause in stem.util.proc, is undefined on Windows. It should fail gracefully rather than raise an exception. I've fixed it, and my public repo is: https://github.com/beckbaibai/stem

However, it's not the only bug. The program can't find tor even though I've installed it. It says "Unable to start tor, 'tor' does not exists." I don't know the reason yet.

Trac:
Username: reganeet