Fix cowboy_websocket_handler callback spec
Replace terminate/2 with terminate/3, adding a Reason

This should have been done a *long* time ago, back when I initially
added Websocket support. This is the first part of two in improving
loop handler support with regards to socket closure.

Reason may include: {normal, shutdown} for the most normal shutdown,
{normal, timeout} for a loop handler timeout shutdown, or {error, _}
if an error occured.
Do not require inets for running tests anymore
Make cowboy_static use universal time
Merge branch 'master' of https://github.com/0x00F6/cowboy