Update parking_lot and lock_api

[cwfitzgerald]

A week or so ago parking_lot updated to 0.11, bringing along with it lock_api 0.4.X. I don't know what would be required to implement this, and due to the increment of lock_api would unfortunately have to be a breaking change.

As of right now, as people are starting to upgrade to newer versions of parking_lot, it's also bringing with it the new version of lock_api, causing duplicate deps and possible trait mismatches.

If you're willing, I can help make progress on this.

[Matthias247]

Should be done with #50