Script to bump version and tag release on master

[rachel-fenichel]

Is your feature request related to a problem? Please describe.

A late step in releasing is to bump the version on master and tag that commit. This should be scripted.

[rachel-fenichel]

Formats:

Master:
Major version number is 3 after the q3 2019 release
major.yyyymmdd.patch

Develop:
Builds off the most recent release to master.
major.yyyymmdd.patch-develop

This complies with semver.

[samelhusseini]

The version in the blockly_compressed is pulled from the package.json.
As part of this change, we should make sure that the version is bumped before a re-build so that the latest version is bundled into the release candidate.