Add a script to populate the DB with sample data

We may not keep this script around forever, but its useful right now.
Merge pull request #15 from markmc/sample-data

Add a script to populate the DB with sample data
Remove unused APICoverage class

This is used in Nova to ensure that VirtAPI has a test per method in the
class. We're not using it in Tuskar now, so let's remove it.
Fixed git URL in README