Send concrete messages instead of random ones

[marcosmercuri]

Added a new parameter messages-data, which is a string with a concrete fix message to send.
This parameter can be repeated as many time as wanted. The messages will be sent one by one, and when the list is finished, it starts again from the beginning.

Example:
$>sangrenel -topic test --messages-data "{\"field1\":{\"field2\":\"value\"}}" -messages-data "{\"field3\":\"value2\"}"

Will send first the "{"field1":{"field2":"value"}}" message, and then "{"field3":"value2"}", and then again "{"field1":{"field2":"value"}}", and so on.

[jamiealquiza]

Great, this is on track with one of the features I never quite got around to. One thing I had in mind was to have special field identifiers that could translate to non-static data, such as a timestamp field or random data field. The timestamp option is self-explanatory, but for the random data field, I was thinking something like a @data[50] sort of specifier that'd result in 50 bytes of random data for that field.

Two things this would solve:

• Partition hot-spots if a routing key is eventually used
• Unrealistically high compression ratios on repeat / static data