More robust linguist path discovery.

Fixes #724 (closed).

In this patch, the path discovery code takes only the last line of the command output and assumes that this is the correct path.

Hopefully you can eventually come up with a better way to do this than running a script and capturing its output, but this change should make the existing method slightly less error-prone.

I've never written any Go before, so if there's a better way to do this, my apologies.