Documentation improvements

[benmccann]

• Combined the installation and integration sections. These sections had basically the same content for loading from a script tag. It's also more coherent for the npm version to put the content together vs refering to two separate sections
• Show that luxon has to be installed separately and is not pulled in as a dependency
• Update the version number on the readme to 0.1.1
• Removed /dist/Chart.min.js from Chart.js CDN link. Sent https://github.com/moment/luxon/pull/468 to improve Luxon CDN setup

[benmccann]

CC @kurkle since https://github.com/chartjs/chartjs-adapter-date-fns/blob/master/README.md follows the same pattern

[simonbrunel]

Thanks @benmccann, I totally forgot about that PR.