changed shape to return Maybe Shape.
added 'trapping'. changed 'assert' to 'preventing'.

There is an 'assert' in Control.Exception that has compiler support to
turn on and off.
Merge pull request #23 from timsears/develop

changed shape to return Maybe Shape.
removed pesky asserts in Contours/Matching.hs
more changes to keep up with hmatrix015
lined up semantics of trapping/warning/preventing.
Merge pull request #25 from timsears/noassert

Noassert
Merge branch 'develop' of github.com:albertoruiz/easyVision