Add parsing tests for the CSS Shapes Specification's shape-outside property
These tests cover the positive test cases for the auto, shape, box, and
box + shape values. They do not cover computed styles (much), or image values
(at all).
Adding tests for initial and inherit values, and some additional cleanup
Merge pull request #396 from betravis/shape-outside-values

Parsing tests for CSS Shapes' shape-outside property