Version 500 and 600 support for id pools ipv4

[jyothisgm]

Description

Version 500 and 600 support for id pools ipv4 subnet and added support for generic class.

Check List

• [X] New functionality includes testing.
  • [X] All tests pass for Python 2.7+ & 3.4+($ tox).
• [X] New functionality has been documented in the README if applicable.
  • [X] New functionality has been thoroughly documented in the examples (please include helpful comments).
  • [X] New endpoints supported are updated in the endpoints-support.md file.
• [X] Changes are documented in the CHANGELOG.