PYCBC-92: User-defined transcoders

This provides the transcoder interface, some more documentation on how
to use it, and an efficient C-based base class.
Change-Id: I2e24aa2431110519575e8ac0c224a511995123d1
Provide exception class to indicate internal SDK errors

Change-Id: Idd8c0cf06f7a2ea64250c9175457aceb6dd0d879
Update .gitignore

Some specific settings for scripts I use

Change-Id: I020072478dd1b484a76cc527772041737992fd5b
Code formatting and naming changes; PEP7

Try to be more in compliance with PEP7, also make some basic type names
shorter. There is precendent for this in other modules shipped with
Python

Change-Id: I5a4147b4f75df9e938d76046b926c53006769462
PYCBC-119: Add bucket property

Change-Id: I37be64714781e6576d8982f9e8525ed886db8488
PYCBC-118: Provide informative __repr__ for Connection

Change-Id: Ie2b3b6be8534e18222698c0c3e108882ee20e0e8