clean up ignore tags code.

Before we do a release on this I decided to clean the code up so its more readable. I also found a bug with widont where it would apply to all non-ignored sections. Because of this—and the fact that widont only runs within a subset of tags—I now run the widont filter after the ignore process.

@barrysteyn and @justinmayer if you guys review and find everything satisfactory I'll merge this and tag a new version.