Merge pull request #21 from davidlmorton/master

Handle array inputs and outputs properly
Better error messages if there is a workflow mistake that causes Moose type constraints to be violated
Merge pull request #22 from susannasiebert/master

Better error messages
Add additional UR dependency (latest commits on UR master need this)
Don't let an undef keep us from seeing other errors
Only create an allocation if there are files to be saved
Update logging
Add object iterator for persistence/amber
Update ur to newer version