Autotools updates

Few autotools updates and de-duplication of the README file.
NOTE: not sure about the readme file if that works on windows this way.

Please remember to run "make distcheck" call to test and then release the source tarballs from the tag :)
I made two readme formats because Windows will always open .txt files, and Markdown format doesn't look so nice on plain-text editors (stuff like escaped underscores, bracketed links, etc). It's not like the Readme is updated that often anyways.
Feel free to only include the most appropriate format on Linux builds though.