Add all-spaces chunk handling in binary/protocol.

Hi Jeanfrancois 

I got all-spaces chunks (i.e. chunks with all bytes being set to 0x20) propagate up to my protocol decoders.

This change to ```StreamTransport``` prevents this from happening - while letting the handshake chunk (that starts off with 0x20 as well) pass on the the decoder you recently added to the AtmosphereRequest object.

Please have a look and let me know what you think.

Cheers, Christian.