My initial goals are seamless connection pooling and reasonable defaults
to make fetching files as easy and reliable as possible. The connection
pool allows a go program to fetch files in parallel in a natural way
(multiple goroutines, a single client). It also adds some restrictions,
though (e.g. changing directies will be off limits for now since you
won't be using a consistent control connection to the server).

So far I've done the connection pool and the initial control connection
setup. I need to figure out my testing strategy.