Release 2.4.0 (rigetti#806)

* Update the changelog for v2.4.0

* Bump version to v2.4.0

* Drop v2.5 reference in changelog, change tpb -> ntpb

Release 2.3.0

Release 2.2.1

Release v2.2.0

Release 2.1.1

Release v2.1.0

Release 2.0.1 docs-only release

Bump pyquil version to v2.0.0

Bump pyquil version to v2.0.0b8

Bump pyquil version to v2.0.0b7