[DO NOT MERGE] Announce community-supported languages

## `travis-build` PRs
1. C#    https://github.com/travis-ci/travis-build/pull/294
1. D     https://github.com/travis-ci/travis-build/pull/340
1. Julia https://github.com/travis-ci/travis-build/pull/318

## Docs PRs
1. C#    https://github.com/travis-ci/docs-travis-ci-com/pull/133
1. D     https://github.com/travis-ci/docs-travis-ci-com/pull/148
1. Julia https://github.com/travis-ci/docs-travis-ci-com/pull/152