README: changed format to Markdown, added credits to author

This pull request essentially changes the format of the main README file to Markdown, to get a better look of the main page of the repository. The commit also adds more information about authorship. The diffstat is the following:

    README    | 47 -----------------------------------------------
    README.md | 42 ++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 42 insertions(+), 47 deletions(-)