Simplified clien_test.go file by testing two different RTP packet operations using loop. We now first test no operation,
and then test a rtp.Payload operation, which gets the payload of the packets and stores them in the client ringbuffer for the
user of the client to read.
Wrote test TestReceiveNoOP to check that client works correctly when we give no operation to perform on RTP packets before
storing in the client ringBuffer, which calling io.Reader implementation Read will get packets form.
Added client.go which contains a struct to describe an RTP client. It provides a method, Start, which will
invoke a recv routine to start receiving packets and process them using an op function passed on the Client's
creation. Client implements io.Reader, so that the client may be read from.
Saxon