Add TLS support

@myleshorton I added a new project [getlantern/tlsdefaults](https://github.com/getlantern/tlsdefaults) that provides sensible defaults and I'm now using that here.  One of the defaults is to specify a minimum TLS version of 1.0, but as you pointed out we control both sides here, so I'm forcing TLS 1.2.

I also moved the cipher suite preferences into tlsdefaults.