Needs to support custom CI commands

[cobyism]

Right now, the project only runs CI by executing script/cibuild inside each project, but it’s obvious that many projects will want different commands to be run instead to execute the bootstrap/test run for their specific project.

This probably requires being able to configure this at the project level, so there’s a couple of ways this could be achieved:

• it might just need a field to be added to each Project where people can specify the command to be run. The downside of this is it lives in the database, rather than in the project itself.
• maybe this project simply mandates a specific file convention (similar to travis.yml) where information about what should be run is stored.

I’m going to say that the later option (mandating a dciy.toml or something) might be the most flexible, simple solution.

[cobyism]

TOML file could be something like:

[dciy.commands]
prepare = ["script/bootstrap"]
cibuild = ["script/cibuild"]

[cobyism]

This is now possible because of #13.