Windows fixes

[bgourlie]

This PR fixes a couple issues:

• The dev server didn't work on windows due to the bundle path being prefix with unix directory separator

• The tests failed due to non-portable environment variables and mkdir and rm commands.

For some reason, npm automatically removed the ^ version constraint from all dependencies in the lock file. The change itself seems to make sense given the purpose of the lockfile, but I can revert it to it's previous state and manually add the new entries if you'd like.

[bgourlie]

Forgot to mention, I tested this on both Windows and OS X.

[rogeriochaves]

Thank you very much for your contribution! And sorry about that, I don't have a windows to test it so I end up overlooking windows users :T