New repo configuration

[etarancon]

• Travis configured to launch the eslint comand to every js file.
• Contributing section, bbva-eslint link and npm version tag added to README.md.
• Jshint deleted.
• .eslintrc file converted to js due to it's deprecated.
• testem.js configured to show tests launched in chrome.

[adrigzr]

:tada: This PR is included in version 0.3.1 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: