Patch objpool.http to support SSL Authentication

Refs #54

The module objpool.http provides pooled connections without SSL
Authentication.
A new connection class is implemented in kamaki.clients.utils.https
The name of the class is HTTPSClientAuthConnection
The PooledHTTPConnection is patched to provide HTTPSClientAuthConnection
instances as https connections.

Also, astakosclient module is patched to use the same https connection class.
Add ignore-ssl and ca-certs options to CLI

Fixes #54

Both options are set either in the config file or as runtime
arguments.

ignore-ssl option allows connections without checking SSL certificates.

The ca-certs option provides a CA file for SSL authentication.

Normally, if no cert files are provided or they are invalid, kamaki
attempts to connect anyway, and an SSL Error ensues.

If ignore-ssl is set to "on", kamaki connects to servers regardless of
the existence or validity of a cert file and all SSL errors are ignored.

To help package maintainers to provide the correct CA file for their platform,
the default path is set in "kamaki/defaults.py" as CACERTS_DEFAULT_PATH