Modifications

[Ffloriel]

As discussed https://github.com/FullHuman/purgecss/pull/78 This PR aims to add:

• [x] tests
• [ ] examples
• [x] continuous integration
• [x] badges to evaluate the state of the repo (build successful, code coverage, dependencies status, ... )
• [x] contributing.md to explain how to contribute to the project
• [x] modify keywords to include remove unused css
• [x] add github templates files (PR and issue)
• [x] add code of conduct
• [x] add information to the Readme (e.g. minimal example to get it to work without looking at the documentation)

I can't add travisci and circleci as I don't have admin access to the repo. It should be straight forward. I am using codacy for the code quality and code coverage. I would recommend it since it's free for open source project. You will need to add the token to circleci so that the code coverage report is sent to codacy. Once done, you will need to modify the links for the badges. I tried to anticipate the links but it's not possible for the codacy badges.

[FoundrySH]

Awesome, this is huge 🙌🏻

[FoundrySH]

I'll get CircleCI and Codacy set up shortly. Thank you for that huge effort.

[FoundrySH]

Updated with CI and badges.

[Ffloriel]

That's great. The only thing left is to add an example project in an examples directory. And to release the new version to npm. I opened the PR https://github.com/FullHuman/purgecss-docs/pull/4 so we can start working on the documentation. The with postcss can be the README without the badges. The example on the Introduction page (README.md) should be a simple working example.