version 2.0

Changelog:

• Added ability to pre-allocate space in to_byte_array
• Added derive mechanisms
• Added tox.ini configuration (
• Fixed install_requires in setup.py
• Added six to requirements.txt
• Bumped version number to coincide with internal version.
• Changed testcases in hsm_managment to skip instead of xfail (saves execution time) if configuration is invalid