Make migration and updates to bootstrapped projects easy

[misterfifths]

See #22 for an example of when this comes up.

Not sure how best to tackle this. I guess there are two options:

1. Make some bitchin' way for this to happen automatically. Would probably entail capturing the options the user entered into tiramisu when the project was created, and then using that to recreate the internal state of tiramisu, and making changes, and running the diff by the user? Seems like this would be nigh impossible to get right.

2. Make some centralized repository of information about migrating (e.g., a wiki). Also start keeping better track of what changes between versions, so users can be aware if they ought to do something.