Windows Support

[jasonvasquez]

Opening a new issue to track fixing issues in Windows support (as seen as a tangential issue in bigtestjs/cli#43)

I have a branch open in my fork (not quite ready for PR yet) that has a couple of the basic issues fixed (primarily in finding various paths, etc.).

Specifically, this commit addresses issues in locating the npx command, and adds an additional path to search for on Windows for chrome. Additionally, I did add a new dependency on the which npm module, so we can avoid shelling out to the which command to find the existence of binaries (and doesn't exist on Windows :))

[Robdel12]

Hey @jasonvasquez, thanks for cracking open this issue! And super thanks for taking some time to fork and patch up some code :)