Our Perl images are now all based on Debian Buster so there is no longer
a need to try and install Jessie packages.

Patch test databases [master]

Source: master branches of all relevant Ensembl repositories as of 10:00
today. This brings all test databases at hand to schema version 100.

The database in question _has_ been patched to 97 and 98 in their
respective release branches but those patches did not make it to the
master branch at the time.

Patch core and ontology test databases to schema version 100

Patch test databases to schema version 99

Travis: explicitly use Ubuntu Trusty for builds

Matthieu Muffato's experiments with ensembl-hive have shown that in
spite of https://docs.travis-ci.com/user/languages/perl/ claiming
Travis supporting perl-5.8 and newer, the oldest version supported under
the Xenial environment is 5.22. This has since been confirmed by a post
on Travis community forums:
https://travis-ci.community/t/failure-with-perl-5-16-5-18-5-20/2458 .

We are presently not ready to drop support for Perl versions older than
what Travis makes available under Xenial, therefore let us for the time
being make sure we continue to use Trusty for now.

Release-98 version bump

For some reason ensembl-io test ontology database went out of sync some
time prior to release 97. See the discussion of PR #85.

Source: release/98 branch of ols-ensembl-loader and master branches
of all other relevant Ensembl repositories, pulled a few minutes ago.
Compara, Variation and ontology schemas all have already been bumped to
version 98.

README: Use the same badge syntax as for 'ensembl'

i.e. explicitly specify the branch

ancestral_allele update to handle Variation API changes.

[ENSCORESW-3077] Travis: Unify configuration of Slack notifications

ensembl Utils::IO into ensembl-io

Looks good to me, the errors are related to th changes to the schema in the ensembl repo which is fixed in a separate PR.