Request Timeouts

[IGJoshua]

Functionality should be added to all rest endpoints which allows timeouts to be specified, such that any request which takes longer than the timeout will be ignored and the promise returned will be realized with a default or user-specified value.

Currently, I think I should edit the defendpoint macro to include a :timeout and :timeout-value parameters. :timeout will be a number or channel, if a number it will create a timeout channel with that many milliseconds, otherwise it will be assumed to be a promise-chan which will yield an item when the timeout is reached.

The defendpoint functions will then spin up an additional go block which will take on that channel and upon receiving a value will put that value or :timeout-value onto the returned promise.

Additionally, make-request! should be updated to throw out a request if the :timeout channel can yield an item.