Windows fixes

Changed to BrowserStackLocal.exe instead of the jar-file.
The tunnel process is now killed when the tests are complete.
Before when using the jar-file the tunnel processes still were alive in the background after the test were completed. Which created problem the next time you ran the tests, your worker then never received the "Acknowledge" state,

Added path fix for Windows, it now works with "/" on Windows in the "test_path" config.

Fixed the Process signals to work on Windows, before you never got to the method "cleanUpAndExit" in cli.js because of how Process.kill works on Windows. It now runs "cleanUpAndExit" before exiting the process as expected.
True, the exists check needs the full file name.

It seems fine to me to just save the file without the extension, shouldn't matter how its displayed in Explorer. I'll leave that to someone from BrowserStack to decide.