juju-core bootstrap change

[Ian Booth]

Hi folks

If you are running from source, you need to be aware of a change made to trunk
and which will be in the next release AFTER 1.13.3.
Previously, when juju bootstrapped a new environment, it would be happy if it
could find tools which matched the major version number of the juju used to
bootstrap. Now, the check has been made stricter and both the major and minor
version numbers need to be consistent with the juju version.

This change should not have any visible effects for most people; developers tend
to --upload-tools and the correct tools are always in place for clouds like
Amazon, HP Cloud, Azsure, MAAS etc. Those people running private Openstack
deployments need to be aware so that they can ensure their tools repository is
up to date (if they do not rely on the S3 public repository).