Add heuristics for automatic rebuilds/reinstalls

[aleclarson]

Inside <rootDir>/.indo-cache, track when local packages were last built. Build any package missing a timestamp. Also, check the "mtime" of the package's lockfile to know if a package should be rebuilt due to changed dependencies.

[aleclarson]

And store the dependency map of each local package in <rootDir>/.indo-cache to automatically update dependencies when indo runs.