refactor(localforage): move driver names and priorities into constants
refactor(localforage): create an enum with the MODULE_TYPEs
Merge pull request #221 from thgreasi/enum-refactor

refactor(localforage): use enums for driver names and module types
Call library methods only when ready
Apply "root" level beforeEach hook to run test suite against callWhenReady API method stubs
Add detailed explanations for callWhenReady and its tests
A bit of OCD ABC cleaning
Add fix from @ahbeng to README's require section
Add automatic ready() call to CHANGELOG
Resolve merge conficts from upstream