Update docstrings and methods in api.py.

Update the references URL in the doctring with the new Twitter API doc.
Fix formatting for :allowed_param in the docstring.
Fix method for destroy endpoints (POST instead of DELETE).
Merge pull request #485 from volnt/patch-1

Update docstrings and methods in api.py.
"cd tweepy" command after git clone in README

Missing "cd tweepy" command after git clone in README.md in installation instructions
Merge pull request #487 from bryant1410/patch-1

"cd tweepy" command after git clone in README
Change the required version of the requirement package requests to solve the version conflict error when installing tweepy from code
Merge pull request #488 from joausaga/master

Update the required version of the requests package (requirement.txt)
fix merge conflicts