Create BoltDB interface

[bbengfort]

Create mechanism to interact with BoltDB including the following buckets:

• [x] Names (matches file names to version)
• [x] Versions (matches version numbers to meta data)
• [x] Prefix (storing directory metadata)

[bbengfort]

In order to support multiple databases, I created a database API as follows:

There is a Database interface that all database drivers must implement. I've currently implemented two drivers, BoltDB and LevelDB. You can specify which driver you'd like in the YAML configuration file, and it is initialized correctly.

All other methods will be "stored" and "fetched" from the database according to the model structs that they represent (for marshaling and unmarshaling of JSON data).

[bbengfort]

TODO:

• [ ] Cursor
• [x] Tests