Deploy monitor

Closes #22 
Closes #19 

Adds a top-like 'Stack Monitor' via `opsicle monitor <environment>`
Currently only a deployments screen is available, but the abstractions around curses will allow us to easily add more in the future. These classes are a modified version of https://github.com/tiredpixel/sidekiq-spy 's process monitor. Some of it could be written a bit differently to better suit our purposes, but that can be handled over time.