Transparent request sending API #153
Description
Currently, it's not clear to user when request is actually sent. On request creation, we simply encode it and put to a request queue. When calling wait, we check if we have received responses, and there is no one, we send pending requests to Tarantool.
Arguably, sending request right after creation seems inconvenient - one might want to batch requests in order to minimize amount of syscalls.
Arguably, sending requests on each wait seems inconvenient as well - one might to process received responses before sending requests to the server.
If choosing between these two, I prefer the second variant.
As an alternative solution, we could add flush method to flush all pending requests manually. Also, we could add autoflush configuration parameter in order to simplify API for those who don't want to batch requests.