Add ESLint

[kesara]

Description

• Add ESLint.
• Add test and lint checks to TravisCI.

Motivation and Context

This repository didn't have ESLint as a dependency. The TravisCI has not been configured to run test or lint.

How Has This Been Tested?

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation change

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read all applicable contributing documents.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [ ] I have updated the change log (if applicable).

[dead-claudia]

I'm going to put this on hold since I'd rather keep it aligned properly with what Mithril proper is doing, so it's less likely to cause unexpected issues.

[kesara]

I'm going to put this on hold since I'd rather keep it aligned properly with what Mithril proper is doing, so it's less likely to cause unexpected issues.

Sure, let me know if you need any help on that.

[pygy]

@kesara thanks for the PR, and sorry for the delay.

This PR is now outdated. Ospec has been a bit neglected, we forgot about this and added eslint ourselves in the mean time. Also, Travis is no more.