client side certificate doc mistake

[OferE]

There is a mistake in the documentation on how to use client side certificate.
The cert, key and passphrase should be given to the "options" object and not to the agentOptions.

I also created a pull request for this:
#1289

I didn't touch the SSLV3 paramters inside the agentOptions, so please also verify if this is the correct place for it.

I hope this helps.

[nylen]

I'm not familiar with these options. We really need to get some tests for them.

[nylen]

Fixed by #1585.