Update to support new Bitstamp API

Updates the private API to support the latest Bitstamp key based API (the old one will no longer function after 31 October 2013).
Adds a few function that previously weren't implemented, so that the full private API is supported.
Merge pull request #1 from vorwrath/master

Update to support new Bitstamp API
Update README.md

Documentation adjusted according to vorwrath pull request.
Tests adjusted for new API
Adjusted README
Issue #2 test added
Issue #3 public part compatible with python 3
trading part testing compatible with python 3
trading part compatible with python 3
Updated documentation
Fix in documentation
Fix in documentation
Fix in documentation
Fix in documentation
Added dictionary result into Readme
Update README.md
Corrected 2 small errors in the example code
Merge pull request #4 from jacopsd/master

Corrected 2 small errors in the example code
Add a Bitdeli badge to README
Merge pull request #5 from bitdeli-chef/master

Add a Bitdeli Badge to README