Install test scripts with automated installer; documentation for certificate errors

Aaron;
This pull request has a few fixes based on review feedback:

- The automated installer and upgrader now keep the test suite up to date and provide pointers on how to run it.
- Have the test script call sub-processes with bash instead of sh, since it is reliant on bash-specific exports. On systems where sh points to other shells (like dash) the export of `check` from master-test.sh does not work otherwise.
- Add documentation about certificate errors for downloading the script. I'm not sure if this captures all potential problems but documents a first potential point of failure on machines with older versions of wget.