Convert between ints and floats when loading numbers

Fix loading of numbers. (#3)

The javascript firestore sdks can convert automatically between integer and floating types.
This updates the loading code to convert between ints and floats.
Based on https://github.com/googleapis/google-cloud-go/blob/27b5416a80e6a65ee9eebda55f06def51b9b7b88/firestore/from_value.go#L119

Fix panic when saving an invalid key property.

v0.1.16

Don't panic saving a property with an invalid key. (#2)

Add array-contains query operator

Add support for array-contains (#1)

* Add support for array-contains
* Add query_test

Co-authored-by: Ryan Brown <ryan@derivita.com>