Support for testing HTTP PUT and POST

[iyesin]

Hello,

I believe it would be nice to have a way to submit pseudo-random buffer (or user-specified static file) to user-specified URLs and measure same set parameters as for GET, plus http_put_seconds{type=ContentTransfer} (keeping http_get_seconds as is for compatibility reasons). WDYT?

[syepes]

Yes this woudl be an interesting feature, the only thing I see is how and what format/type of data we shoud send but specially what backends/enpoints could be supported for the reception of the payload.

I would be open for PR :-)