Issue 815, 1407 EarClippingTriangulator

previous pull request for issue 815 ( with description ) - https://github.com/libgdx/libgdx/pull/326
issue 1407 -  'minArea' - value for most accurate calculations ( must be a negative and should be close to zero ). It's need here because may be returned a small mistakes in concave / not concave by #getCrsArea. For this case i use a 1.0E-7 ( and this will be default ). In other cases where vertices are not so nearly 'minArea' can be changed to zero. I think this a most simple and **optimal** decision.