If you want to contribute, here are a few things to keep in mind to make sure your patch is consistent with the rest of the module.
To get started, run
git clone https://github.com/skovsgaard/exleveldb
then, run
mix do deps.get, compile, test
to ensure you have a working build (discounting any bugs you may be fixing).
From this point, create a descriptively named, snake_cased branch, e.g.
git branch test_fixes
git checkout test_fixes
Then, you should be ready to get to work.
Luckily, a great style guide for Elixir already exists, so if you just follow that, you should be fine.
Lastly, before you commit (or more importantly, before you send the pull request), make sure your tests are passing and that - if you are adding new functionality - you have included tests covering it.