Python hvac

IMPROVEMENTS:

• New KV secret engine-related classes added. See the KV documentation under hvac’s readthedocs.io site for usage / examples. GH-257 / GH-260

MISCELLANEOUS:

• Language classifiers are now being included with the distribution. GH-247
• Token no longer being sent in URL path for the Client.renew_token method. GH-250
• Support for the response structure in newer versions of Vault within the Client.get_policy method. GH-254
• config and plugin_name parameters added to the Client.enable_auth_backend method. GH-253

Thanks to @ijl, @rastut, @seuf, @downeast for their lovely contributions.