This commit fixes a small error introduced in a previous commit. Servers
given by command line options weren't being added to the configuration
because we were checking for `iceServers` to be nil instead of not nil.
Modified the snowflake client to use pion/webrtc as the webrtc library.
This involved a few small changes to match function signatures as well
as several larger ones:
- OnNegotiationNeeded is no longer supported, so CreateOffer and
SetLocalDescription have been moved to a go routine called after the
other peer connection callbacks are set
- We need our own deserialize/serialize functions
- We need to use a SettingEngine in order to access the
OnICEGatheringStateChange callback
MaxBytesReader is only documented for server side reads, so we're using
a local limitedRead function instead that uses an io.LimitedReader.
Declared limits in a commented constant
