updated raxml version to 8.1.8
updated release number for module package
added raxml 8.1.11
Merge pull request #2 in APS/raxml-roll from feature/APS-61-upgrade-raxml-version to master

* commit '3f32cb7a984b29061c3ae743314d481c38b41529':
  added raxml 8.1.11
  updated release number for module package
  updated raxml version to 8.1.8