Fixed the scenario hazard calculator
Fixed the ipython notebook
Improved a log message
The export_dir is now mandatory
The export_dir is optional again
Better error message for regions that cannot be discretized
Refined the check is_valid_export_dir
Fixed test_invalid_export_dir
Changed test_invalid_export_dir to make Jenkins happy
Merge pull request #64 from gem/wrong-discretization

Better error message for regions that cannot be discretized
Merge pull request #62 from gem/scenario-hazard

Small fixes to commonlib
Merge pull request #63 from gem/check-export-dir

The export_dir is now always given
Added a BaseHazardCalculator
Merged from master