Hotfix: `TemplateNotFound` Issues

This pull request fixes FLY-43 (which corresponds with GH #35), wherein constructing a `ModuleLoader` for templates where the root template package doesn't exist yields a `TemplateNotFound` error.

The new behavior is:
1) If `force_compiled` is on, force an `ImportError`
2) If `force_compiled` is not on and there are source templates, simply use those

Everything is still covered by tests and junk.