.travis.yml: use regex to also build on tags
.travis.yml: use regex to also build on tags

apparently, Travis identifies tags as 'branches', thus we need to include any branch whose name resembles a release tag (e.g. 'v1.0'), or else those builds are skipped with an error message:

> Branch "1.1.0" not included per configuration

googlei18n/cu2qu,fonttools/fonttools,googlefonts/cu2qu,googlefonts/fonttools