Fix ChannelBind response

Resolves pion#71

tagging

Fix race in server shutdown

Add lock around server socket

Add graceful shutdown for allocations

Tear down all allocation when server is closed

Bump pion/stun

Also drop go-spew

Add Create/Close methods to server

These are needed for E2E test pion/ice

STUN v2 migration

Migrate to new STUN API

FireFox now works with pion-TURN

We were creating a reservation for every request (this is incorrect) a
reservation should only be created when EVEN-PORT is supplied.

FireFox would reject our STUN packets because it failed to comprehend
the reservation attribute

Comment exported functions from allocation package

Fix Windows networking

After a short time if :0 is used (instead of 0.0.0.0:0) the following
error would be printed

```
err: write udp [::]:50147->172.31.22.172:50149: sendmsg: The system detected an invalid pointer address in attempting to use a pointer argument in a call.
```