Bumped version to 7.4.0 (firebase#534)

Bumped version to 7.3.0 (firebase#506)

Bumped version to 7.2.0 (firebase#490)

Using the correct message copies in sendAll() API (firebase#480)

Bumped version to 7.1.0 (firebase#476)

Bumped version to 7.0.0 (firebase#451)

Bumped version to 6.5.1 (firebase#446)

Bumped version to 6.5.0 (firebase#439)

Bumped version to 6.4.0 (firebase#419)

Bumped version to 6.3.0 (firebase#399)

* Bumped version to 6.3.0

* Updated changelog