Milestone: project deployment from Git

Minimally viable version of Fabricator should be able to:
1. Connect to a configured host via SSH
2. Ensure there's a Git repository checked out from configured commit/refspec at a configured location (e.g. there's a directory `/opt/emulsion` cloned from tag `v1.1.2` of Emulsion GitHub repository)
3. Ensure that the contents of a configured file (e.g. `/opt/emulsion/config.json`) correspond to a configured value
4. Perform a command on each run (e.g. `docker-compose up`)