clean up terrible Path-str-String handling

[Fishrock123]

The Path <- str -> String logic littered all over the place from the addition of bundling should probably be cleaned up.

It's a mess and full of .unwrap()s with potential panics. For many of these spots it may be better to handle using OsString, some Path crate, or something else from the stdlib that I am missing.

[creationix]

Stuff like this is why I bought tickets to rustconf and signed up for the workshops. I'm hoping that I will understand more best practices.