Add option to search filesystem paths as well as git.

This patch also updates both the CLI and JSON interfaces to support
filesystem scans.

Work still to be done: rework API/interface to be more informative
about filesystem paths. Right now it's using a dummy repo which causes
extraneous info to show up in results.
Merge pull request #1 from ternus/fs-scan

Add option to search filesystem paths as well as git.