- Common pre-commit config from snippet.
- Migrate from Travis CI to GitLab CI.
- Convert README from reStructuredtext to markdown.

Point to the new GitLab instance.

- Use types instead of files regex, set minimal version of pre-commit to
0.15.0 accordingly.
- Now that the minimum version of pre-commit is 0.15.0, remove legacy
hooks.yaml file.
- Updated README.
- Bumped minore version.

- Use shellcheck from cabal instead from the Ubuntu package repo (which
has a newer version that supports --external-sources).

checked by shellscript (in case the modification is only in the calling
script the test will fail since only the modified script is checked).
- Bumped patch version.

- Bumped patch version.

script listed.
- Bumped patch version.
- Added pre-commit hooks to test the shell-lint script added.

variables set).
- Bump minor version.

- Cache pip and pre-commit in TravisCI.

.pre-commit-hooks.yaml, update pre-commit-config.yaml accordingly.
- Set pre-commit hooks by version tag instead of hash.
- Bump minor version.