Dexie v3.0.0-alpha.1

This is the first release after refactored dexie to typescript (Announcement #622, PR #653).

In summary, everything should work the same as latest stable, version 2.0.1.

To install:

npm install dexie@next

Keeping it on new major due to the massive rewrite and possible backward incompatibilities in the typings file (should only concern typescript users though). The only 2 known incompatibilities are:

1. When using dexie-relationships from a typescript perspective. It may not be able to declare the typings of extended table and collection methods correctly.
2. Requires a newer Typescript version (2.6.1 tested) to understand the d.ts file.