fix (delimitedProtocol): add check for transport

Add check for this.transport before attempting to write it. This could
be done at the base protocol layer but this approach matches the
other methods in the base protocol check for this.transport instead
of ensuring it exists.
Merge pull request #67 from gameclosure/fix-delimited-protocol-with-no-transport

fix (delimitedProtocol): add check for transport