Support TLS_PSK_WITH_AES_128_GCM_SHA256 (Philips Hue Entertainment API)

[daenney]

In the same spirit as #45, I'd like to add support for TLS_PSK_WITH_AES_128_GCM_SHA256 which is what Philips uses for the new Hue Entertainment API.

Given we already have PSK support thanks to @Sean-Der's efforts on #45, #76 and we already have AES_128_GCM_SHA256 I suspect this should be relatively straightforward.

I'll take a look at this in the coming weeks, just wanted to file an issue here so it's tracked somewhere.