Update README.md

## Formatting
It's a good practice to have a H1 title and the build status button on top of the readme.

## Updated instructions for using the sample project
Previous instructions had git submodule, but I could not find a submodule in current code version, but I found a Podfile, so I updated instructions for using it.

## Removed duplicate information.
The "optimized for WordPress feeds" was duplicate.

Hope it helps, the project will help me in a project, so I'm trying to give something back. Thanks for your great work!