Tests to reproduce bug found by Peter D. Gray.

See https://github.com/richardkiss/pycoin/pull/1
Fix test failures.
Fix another Python 2.7-only problem.
Prep for 0.23 release.
Don´t use distutils. Fixes #3.
Merge pull request #4 from manpages/master

Don´t use distutils. Fixes #3.
Add John Mostovoy as contributor.
Make byte prefixes depend on network type. Fixes #2.
Make public_byte_prefix & private_byte_prefix more Pythonic.
Add tests for testnet wallet generation.
Bugfix: on py2.7 only, to_bytes_32() would return less than 32 bytes for any int < (2**256)