Fixes for windows paths

[KrekkieD]

Using an absolute windows path (i.e. d:\test\test) it would fail silently. Checks on path.sep will not work if a unix-based path is given on a windows environment. Made changes accordingly and updated tests accordingly.

It seems it should be possible and easier to make more use of the node path class, but not sure why that was not done so left that alone.

Tests pass on both windows and unix (mac).

Oh, also added option to run tests using npm run test without having mocha on command line.