Update to support RANDOM.org JSON-RPC Release 2 and Python 3.

[Tantusar]

Added:

• Support for RANDOM.org JSON-RPC Release 2 including:
  • Integer sequences
  • Retrieving results of previous signed requests
• Support for Python 3.6+

Removed:

• Support for RANDOM.org JSON-RPC Release 1

Changes:

• Response split into separate class, is returned as is rather than parsing immediately.