This PR does the following:
* moves code coverage generation to happen when `COVERAGE` environment variable is present.
* makes integration tests run when when `INTEGRATION_TESTS` is present.
* moves `ruby-head` from TravisCI build. Previously the configuration allowed for `ruby-head` to be ignored if it failed, but it conflicted with the gem release build job step.

Adds integration tests to the project that's able to run in CI across different ruby versions.

* Adds a Rails 5.2.4.1 app
* Adds a Rails 6.0.2.1 app

Fixes #733 

* Update rubocop requirement from ~> 0.67.2 to ~> 0.68.1

Updates the requirements on [rubocop](https://github.com/rubocop-hq/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop-hq/rubocop/compare/v0.67.2...v0.68.1)

* Rerun rubocop --auto-gen-config

The cop Layout/IndexHash was renamed to Layout/IndentFirstHashElement
causing CI to fail. By rerunning the config generator this updates the
correct cop name so that Rubocop no longer fails in CI.

Updates the requirements on [ruby_dep](https://github.com/e2/ruby_dep) to permit the latest version.
- [Release notes](https://github.com/e2/ruby_dep/releases)
- [Commits](https://github.com/e2/ruby_dep/compare/v1.3.1...v1.5.0)
Signed-off-by: dependabot[bot] <support@dependabot.com>

* Update rubocop requirement from ~> 0.46.0 to ~> 0.67.2

Updates the requirements on [rubocop](https://github.com/rubocop-hq/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop-hq/rubocop/compare/v0.46.0...v0.67.2)
Signed-off-by: dependabot[bot] <support@dependabot.com>

* Make changes to let Rubocop pass in CI

* Update rubocop requirement from ~> 0.46.0 to ~> 0.65.0

Updates the requirements on [rubocop](https://github.com/rubocop-hq/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop-hq/rubocop/compare/v0.46.0...v0.65.0)
Signed-off-by: dependabot[bot] <support@dependabot.com>

* Regenerate .rubocop_todo.yml

* Drop support of Ruby < 2.2

Fixed some offenses

* Added new gems.

* Fixed Posgresql index tables with `public`.

Added indexes test.

Added test not crash getting indexes.

* Updated rake and rubocop.

 - Replace SpaceAroundKeyword with SpaceAfterControlKeyword
 - Use an explicit rubocop version to avoid breakages during PRs

Reduced the Cyclomatic complexity.
#330 By default didn't annotate activeadmin models.
This close #330

Added coveralls and code climate gems.

Added Simplecov.

issue 36 fix: warn about macros, to mitigate when we're included during a production run, not just a rakefile run -- possibly at the expense of too much noise