Fixing delays of messages in a pipeline

[synweap15]

Fixes #206.

The delays of messages in the pipeline were ignored, only the delay parameter of pipeline's run method was taken into consideration.

This PR fixes the handling of delay parameters of messages in a pipeline (first and all following). In addition in alters the behavior of the delay parameter of pipeline's run method, so that:

1. If there's either a delay specified for the first message or there's a delay specified in pipe run invocation, take the one that's present.
2. If they are both present, take the one that has higher value.

[Bogdanp]

Thanks!