Update header comparison, update readme and add tests

[luckyvs1]

• Add support for case insensitive comparison of header parameters
  • Previously running the following statcode cache-control would return the following error Sorry, statcode doesn't recognize: cache-control
  • After changes the following statcode cache-control will return the same results as statcode Cache-Control
• Add pytest to test functionality of parameters can execute using pytest test_parameters.py
• Update readme to reflect header functionality

[luckyvs1]

@shobrook - would you be able to review these changes when you have some time? Thanks