1.1.1

Changes:

• add xo test
• add Gulp build / release file
• add Travis config + autodeploy
• move Chrome source code in "src/"
• delete old Firefox extension code (deprecated)
• clean Git ignore file

2 goals with this PR:

1. WebExtension: Turn the extension compatible with WebExtensions, and available for Firefox
2. Automation: automatically build and deploy extension to stores with Travis