The recommend way to install is over [pelican-themes](https://github.com/getpelican/pelican-themes).
The `master` branch is the development branch. If you're happy with fresh new things and maybe sometimes (~most of time~) broken things you can clone the `master`, but I would recommend to you to clone a tag branch.
Release 2.0 will include [Translation Support](https://github.com/alexandrevicenzi/Flex/wiki/Multi-language-support). In order to use Flex you need to configure your `pelicanconf.py` to support i18n. See [Multi language support](https://github.com/alexandrevicenzi/Flex/wiki/Multi-language-support) for examples.
Always open an issue before sending a PR. Talk about the problem/feature that you want to fix. If it's really a good thing you can submit your PR. If you send an PR without talking about before what it is, you may work for nothing.
As always, if you want something that only make sense to you, just fork Flex and start a new theme.