stdin API for glide.process

[RobertCraigie]

The biggest limitation with the glide.process APIs right now is likely the fact that communication with the process is uni-directional, you can just lazily read stdout / stderr, but you can't communicate back (yet).

There should be some way to specify the stdin that gets sent to the process, either as a complete string upfront or lazily, likely with some sort of WritableStream setup