Eagerly read config file

[dherman]

I'm thinking maybe we shouldn't lazily read the config file, since it means we can get late errors after Volta does some work. It's probably best to just fail out immediately if there's an error reading the config file.

Thoughts?

[chriskrycho]

After a quick perusal from reading the source, I think this is still a good and needed improvement. For anyone interested in implementing it, the basic strategy would be that instead of having a LazyProject (which is just a lazycell::LazyCell wrapping a Project), we would want to eagerly instantiate that, probably behind a std::cell::Cell to get the same basic semantics as we have now (i.e. runtime rather than compile time borrow checking for simplicity).