Release 1.1.7 changes.md update (ReactiveX#4184)

* Release 1.1.7 changes.md update

* Mention last 2 PRs merged

1.x: Release 1.1.6 CHANGES.md (ReactiveX#4008)

Release 1.1.5 CHANGES.md update (ReactiveX#3913)

Release 1.1.4 CHANGES.md (ReactiveX#3906)

Merge pull request ReactiveX#3846 from akarnokd/Release_1_1_3_changes

1.x: Release 1.1.3 CHANGES.md update

Merge pull request ReactiveX#3778 from akarnokd/Release1_1_2

1.x: Release 1.1.2 CHANGES.md update

Merge pull request ReactiveX#3695 from akarnokd/Release1_1_1

Release 1.1.1 changes.md

Merge pull request ReactiveX#3553 from stealthcode/changesmd-v1.1.0

Update CHANGES.md for v1.1.0

Merge pull request ReactiveX#3551 from stealthcode/changesmd-v1.0.17

Update CHANGES.md for v1.0.17

Merge pull request ReactiveX#3517 from ReactiveX/changesmd-v1.0.16

Update CHANGES.md for v1.0.16