Allow to connect to Kuzzle via SSL

[benoitvidis]

For the time being, the php sdk forces an http only connection.

We should give the ability to connect to ssl.
Additional configuration options are very likely to be required too:

At the very minimum:

• ssl version support
• certificate check (CURLOPT_SSL_VERIFYPEER)

Other CURLOPT_SSLxx may also be required.