added stop-promise to socks-rtc-net

 * Added promise support for when socks-rtc stops (e.g. peer-connection breaks or is closed by remote peer).
 * Added declaration files (*.d) for socks-to-rtc and rtc-to-net
 * Made typescript sym-links done by file, not directory (improves support for `cd` then `tsc` testing). 
 * rtc-to-net now has 'close' as public
 * churn is now used by semantic versioning