Update typescript Promise definition (#518)
Update typescript Promise definition (#518)

Update Promise from this file https://github.com/Microsoft/TypeScript/blob/v2.1.4/src/lib/es2015.promise.d.ts because the current definition seems not compatible with typescript 2.3 PromiseLike definition.
For example :
```typescript
await Promise.all([dexiePromise1, dexiePromise2])
```
does not currently return the same type between typescript 2.2.2 and 2.3.1 without this change.
dfahlander/Dexie.js,jimmywarting/Dexie.js,dfahlander/Dexie.js,chrahunt/Dexie.js,chrahunt/Dexie.js,jimmywarting/Dexie.js,jimmywarting/Dexie.js,jimmywarting/Dexie.js,chrahunt/Dexie.js,dfahlander/Dexie.js,chrahunt/Dexie.js,dfahlander/Dexie.js