Fix binary decoders

[jeremyrsmith]

I did this because many of the binary decoders were incorrect.

• Remove existing binary decoder tests and replace with integration tests against postgres (To verify that they do actually decode the actual PG binary representation)
• Update existing binary decoders for date/timestamp/time, string, and json
• Add hstore decoder
• Add numeric decoder

[codecov-io]

Current coverage is 83.13%

Merging #72 into master will decrease coverage by 3.83%

@@             master        #72   diff @@
==========================================
  Files            18         18          
  Lines           760        836    +76   
  Methods         748        819    +71   
  Messages          0          0          
  Branches         12         17     +5   
==========================================
+ Hits            661        695    +34   
- Misses           99        141    +42   
  Partials          0          0          

Powered by Codecov. Last updated by 0161b7c...63088d4

[penland365]

All of this looks great! I'm super excited to accept a PR for this :) . If you can delete those unit tests that aren't being called, I think this is ready to go.