Release Zulip Server 3.2

shared: Bump version to 0.0.3.

Release Zulip Server 3.1.

version: Update version following 3.0 release.

Release Zulip Server 3.0.

Release Zulip Server 3.0-rc2.

Release Zulip Server 3.0-rc1.

Release Zulip Server 2.1.7.

docs: Change next planned major release to 3.0.

After some discussion, everyone seems to agree that 3.0 is the more
appropriate version number for our next major release.  This updates
our documentation to reflect that we'll be using 3.0 as our next major
release.

Release Zulip Server 2.1.6.