Allow additional riakpbc options like parse_values

[Downchuck]

riakpbc has additional options which could be passed through on the createClient call. A particularly useful one is the parse_values option, which turns on and off the parsing of values vs the returning of a raw buffer.

[Downchuck]

The connection method is kind of a mess, could be cleaned up. It's hard to tell that options can be passed in: https://github.com/LeanKit-Labs/riaktive/blob/master/src/index.js#L18