Update collider_test.go websocket dependency.
Update collider_test.go websocket dependency.

The websocket hosted on code.google.com no longer exists,
which breaks our Chromium bots in
https://build.chromium.org/p/chromium.webrtc/waterfall

BUG=http://crbug.com/567598

webrtc/apprtc,webrtc/apprtc,samdutton/apprtc,bpyoung92/apprtc,bpyoung92/apprtc,bpyoung92/apprtc,samdutton/apprtc,samdutton/apprtc,webrtc/apprtc,samdutton/apprtc,webrtc/apprtc,samdutton/apprtc,webrtc/apprtc,bpyoung92/apprtc,bpyoung92/apprtc