We are using Swiftlit along with Travis in our project, so you should better have swiftlint installed locally on your machine before contributing. Don't be afraid, it's really simple to install. Just run brew install swiftlint. If you don't have homebrew installed - run ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" firstly.
In order to manually run autocorrection, print swiftlint autocorrect in the project folder via terminal. However, every time you build the project this command will be called automatically.