Merge pull request #3 from rbayliss/patch-1

Document strange behavior when running as user

Author: lmakarov

README.md

@@ -57,6 +57,10 @@ Both SlimerJS and Firefox ESR (extended support release) are installed in the co
 `backstop openReport` is not (yet) supported.  
 You will need a running webserver to view HTML reports generated by BackstopJS.
 
+When running SlimerJS, the user you are running the container as must have a home directory in order for Slimer to start properly.  You can work around this by setting the HOME variable.  Ex:
+```
+docker run --rm --user 1000 -e HOME=/tmp/home docksal/backstopjs test
+```
 
 ## Debugging