Bug fix to handle a very rare situation where a successful run is recorded but stderr output is generated as well e.g.  a Python SyntaxWarning from misuse of a global declaration.
Change warning message when no test results available to include possibility of an empty response.
Several small final changes for the V1.0 beta release, including: increasing process limit in the null sandbox to reduce the risk of out-of-thread/out-of-process errors; fix problem of orange ticks in questions with part marks; lots of changes to README.md.