Update version to 0.3.3-SNAPSHOT for further development.
Implement support for operation without core.cache.

- Check for presence of core.cache at runtime and use a stub object that prints errors if it's not present.
- Implement tests to ensure that errors are presented when the user is attempting to use the package without core.cache.
- Implement tests to ensure that you can "get by" using a map for a cache.
- Freshen some dependencies.
Update Readme with information about how to use Stencil without core.cache.