Add EPL license text

Hi,

I've packaged aether-connector-okhttp for Fedora. As part of the review process for getting new packages into the Fedora repositories, we query upstream maintainers (you!) to include license text in source code repository, if it doesn't exist. Apart from meaning that we won't have to carry the license file for the package externally, I also think it's a good thing to have in any free/open source project. :)

If you have any questions or comments about this package in Fedora, please don't hesitate to contact me.

Thanks for making this software!
Gerard.