Catch & log truncated bundles before NSData crashes

If we get a bundle larger than GCDAsyncUdpSocket's buffer, the socket will truncate it without warning. This can lead to us trying to read past the end of the buffer based on the bundle's metadata. This patch causes the rest of the bundle to be dropped and only the complete packets returned with the OSCMutableBundle.
Set udpSocket's maxReceiveIPv4BufferSize to UDP limit

The default is set fairly low (~9200b). It might be an idea to expose this configuration so that applications can specify the expected max size of their bundles. 64k is pushing it, and IP fragmentation will already be causing problems of its own.