Update readme
Update readme

- Update docker instructions

- More or less remove warning not to use sipa

MarauderXtreme/sipa,fgrsnau/sipa,agdsn/sipa,lukasjuhrich/sipa,lukasjuhrich/sipa,MarauderXtreme/sipa,lukasjuhrich/sipa,agdsn/sipa,lukasjuhrich/sipa,agdsn/sipa,agdsn/sipa,fgrsnau/sipa,MarauderXtreme/sipa,fgrsnau/sipa