Add official support for using httplib (as opposed to winhttp) when running on Windows.  You can now use .pem file certificates on all platforms.  winhttp is still used when the user passes in a certificate that's not a .pem file (assumed to be windows certificate store).

Add missing tags for 'Programming Language :: Python :: 3' and 'Programming Language :: Python :: 2' in setup.py (they should be present according to https://python3wos.appspot.com/)

Refactors some of the test init code, and makes some of the credentials json file entries optional.  Renames option to override the use of httplib/winhttp to more appropriate name given we have auto detection.

Readme changes: Additional documentation for management service, and replaces examples of blob storage with the new high level functions.