Added 'ipad' in useragent check.
Merge pull request #370 from TomCorwine/master

Add iPad check in useragents.py
Merge branch 'master' into sprint-branch
Removed unnessary import and added support for hmac.digest_compare
Improved to_bytes functions and removed some useless warnings.
Added PBKDF2 tests
Added PBKDF2 test for default key length
Fixed easteregg
Removed unnecessary import
Removed support for fix_headers which was deprecated for long.
Added PlainRequest and StreamOnlyMixin
Added missing changelog entry
Removed more deprecated functionality
Force evaluation of starmap so that it does not exhaust the stack
Fixed last commit breaking on 2.x
Added missing functions to the security utils page in the docs
Added request.close() method
Removed HTTP constants out of _internal module
Some tiny simplification for chunk iteration
Removed support for non-silent limited streams