Merge remote-tracking branch 'upstream/hydro-devel' into hydro-devel
Check error conditions in path offsetter.
Check polygons for errors and other error conditions during process path generation.
Merge remote-tracking branch 'upstream/hydro-devel' into check_offset_results
Merge pull request #16 from dpsolomon/check_offset_results

Check for various errors that could create malformed paths.