Better error messages for the case where the user hasn't
configured /etc/sudoers correctly to allow "sudo -u mytardis /usr/local/bin/_myapikey" etc.
Minor update to error message for failure to retrieve API key.
Fixed bug introduced while adding more informative error messages
where mytardisfs fails to retrieve a user's API key, and added
a log message if the first API query returns an unexpected HTTP
status code.
Merge pull request #17 from wettenhj/master

Better error messages when mytardisfs fails to retreive user's API key