Add getRemoteCertificates(); to DTLS

[robin-raymond]

$related #66

Add getRemoteCertificates();

interface RTCDtlsTransport {

 sequence<ArrayBuffer> getRemoteCertificates();

 //... more stuff as needed

};

[aboba]

Progress on this issue is awaiting the next WebRTC 1.0 editor's draft, which will either include getRemoteCertificates() or not. The ORTC API draft will adopt whatever ends up in WebRTC 1.0 in this regard.

[aboba]

Added in the latest editor's draft:
http://ortc.org/wp-content/uploads/2014/06/ortc.html