Documentation improvements for the matching module
The docstring for the //whoosh.matching// module does not end up in the HTML documentation because it is written //after// the imports in the source file, which means it was no longer recognised as a docstring since those always have to come //first//.
Please find attached a patch that fixes this. While at it, I also took the opportunity to
- fix a few grammar issues;
- add some more hyperlinks to referenced classes and methods;
- perform some typographical and stylistic nitpicks; and
- remove trailing whitespace.