configurable channel options

[tanner0101]

Make the ClientBootstrap channel options configurable.

[weissi]

@tanner0101 / @artemredkin does this need to be in the 1.0.0 milestone, ie. would it break API? I don't think so but would like to double check with you.

[weissi]

I created a 1.1.0 milestone and I think we should probably move this as we should ramp down 1.0.0 development.