Thrift: Support for Default Headers and SSL

The rationale behind this is pretty much the same as in #1:

Many people use Elasticsearch over unsecured networks that requires encryption and authentication.

Added support for using a SSL-based Thrift socket. Since thrift has no support for authentication in it self, I added the ability to set some default headers on the ``RestRequest``s, which is on par with HTTP-like interface of the Elasticsearch Thrift services. This enables, but leaves authentication as an implementation detail in the Thrift server-side, as it likely should be.

I tried to put some consideration into the argument names, but I'm not 100% sure whether they should be prefixed with ``thrift_`` or not, so I left that in.