When installing a package's dependency, we should iterate through each package source looking for the dependency. For example, if I set up a local package source c:\packages and put my ReallyCool.nupkg package in there, and that package depends on "Ninject", when installing ReallyCool, we should be able to find Ninject in one of the other package sources.
Order of fallback:
- Look in specified feed (if specified via -Source).
- Look in default feed.
Look in all others.