Add tests for duplication in find_intersections.
Add tests for duplication in find_intersections.

dopplershift/MetPy,Unidata/MetPy,ahaberlie/MetPy,ahaberlie/MetPy,Unidata/MetPy,ShawnMurd/MetPy,jrleeman/MetPy,jrleeman/MetPy,dopplershift/MetPy