Allow non-browser websocket clients to access the /logs endpoint

[semk]

websocket.Handler.ServeHTTP serves to browser requests and was also causing logspout to crash when accessed by a client like wscat as they don't typically set the origin header (See https://github.com/gliderlabs/logspout/issues/412). This change bypasses the validation for origin header.

[michaelshobbs]

Thanks for the contribution. Thoughts on a unit test or two for this and the package in general?

[6r17]

Hei ; the error is sill happening and non-browser client seem to have a problem using the ws endpoint