Prototype optimization: server>clientS push buffer
Prototype optimization: alternative send buffer approach
NB: Improve Ajax server>clientS push reliability mechanism

Prior design had a fault that exposed a ~300ms window during which
pushed events could be dropped on the floor.

When hk-ch puller pulled an active-but-soon-to-close-hk-ch, it'd
mark the client's uuid as satisfied despite its send actually being
a noop.

The solution here is to move the `send!` itself into the reliability
mechanism so that:
1. Http-kit's `send!` result can be inspected before acknowledging a
   client uuid as satisfied.
2. Any pulled hk-ch's are consumed immediately, dramaticly decreasing
   the probability of a channel closing before consumption.
Misc housekeeping- emphasis on docstrings, etc.
Bump dependencies
Update example project
v0.9.0-SNAPSHOT