Backoff configuration via ConnectOpts

[travissalascox]

Hi all, had a quick question/request that i was hoping i could get some input on.

I see you use the the exponential backoff from the backoff package. i know this package has a number configuration settings for the exponential backoff and was wonder if it would be possible to "bubble up" some of those options via something like the ConnectOpts (or anything really).

the main driver for this would be the desire to have a little more control over the Max elapsed time in a place like https://github.com/GoRethink/gorethink/blob/master/cluster.go#L228 and maybe have more control over the interval time itself.