Add ability to use custom parameters;

[f100024]

How to use it example:

r = svn.remote.RemoteClient(self.svn_repo, 
                            username=self.svn_username, 
                            password=self.svn_password,
                            custom_params="--trust-server-cert-failures=unknown-ca,cn-mismatch,expired,not-yet-valid,other")

[coveralls]

Coverage decreased (-0.07%) to 77.992% when pulling 0c845d09ad3496487a4f6afc2547327886b35ffe on f100024:feature/add-custom-paramters into 378406505ee854218bd6233b01b49ea8a0d08861 on dsoprea:master.

[coveralls]

Coverage decreased (-0.07%) to 77.992% when pulling 0c845d09ad3496487a4f6afc2547327886b35ffe on f100024:feature/add-custom-paramters into 378406505ee854218bd6233b01b49ea8a0d08861 on dsoprea:master.