Adding ESLint, Prettier and CircleCI Support

[gvarandas]

Problem

The project currently did not have any way to guarantee the coding standard and best practices. This is being discussed in issue #3.

Solution

The integration of some tooling to help the developers to keep their attention where its needed: solving problems.

Steps

• [x] Added ESLint;
• [x] Added a NPM script to run the lint task;
• [x] Added Prettier;
• [x] Integrated ESLint and Prettier to work altogether via plugins;
• [x] Added a pre-commit hook that validates JavaScript files to ensure only code without problem is being pushed;
• [x] Added a CircleCI configuration to trigger builds that run the lint task.
• [x] Solved all linting issues beforehand (added a couple no-unused-vars exceptions due to the usage of the global namespace. This will be addressed in a future change).

Continuous Integration

Even though there is a CircleCI configuration file, the integration to the external tool must be done by the owner of the project.

The config steps are detailed here.

Also, CircleCI supports open source projects by allowing multiple containers to run the build jobs and it is also possible to configure which branches should trigger the CI (or even if PRs should also do it).

The Open Source configurations are here and I can also help with that if needed.

[cuducos]

Even though there is a CircleCI configuration file, the integration to the external tool must be done by the owner of the project.

Just added the repo to Circle CI and it's working for this PR already (failing though). Gonna take a look a better later, but anyone feel free to jump in.

[gvarandas]

Just updated the PR with the no-unused-vars exception. This is necessary due to the usage of the global namespace. Im planning to submit a PR next to also refactor this (and remove the exceptions).

[cuducos]

Awesome, many thanks, @gvarandas ; )