Add new test for indirect parent matching
Add a bit about the design of sterling to the README
Improve code thanks to comments, and add new test
Change variable name
Merge pull request #2 from doctormo/master

Add new test for indirect parent matching
Merge pull request #3 from zenhack/readme

Add a bit about the design of sterling to the README
Change the (outdated) names of some identifiers.

Frames and Widgets used to be the same thing (which was a weird
situation). Now they're not, and the code was dealing with frames but
calling everything widgets.