ReadMe.md to ReadMe.adoc

Prefer Asciidoc formatting for the ReadMe file

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/pastecs@15 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Added license info in ReadMe.adoc

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/pastecs@16 edb9625f-4e0d-4859-8d74-9fd3b1da38cb