Made the Dimension' constructor strict in all its fields.
Added a simplification rule for dimensional division, and a convenience operator for dimensional inversion.
Added US customary units of liquid volume measurement.
Merge pull request #25 from dmcclean/strict-term-level

Made the Dimension' constructor strict in all its fields
Merge pull request #28 from dmcclean/us-volumes

Added US customary units of liquid volume measurement.
Merge pull request #26 from dmcclean/inverse

Added a convenience operator for dimensional inversion
Port to NumType-DK 0.3.
Redo Show per Doug\'s comments on 1134a98
Export siUnit instead of Dimensional constructor.
Merge latest from bjornbm/master.
Naming changes.
Hide dmap when importing the prelude.