Add `Attrs` class to `genshi.core.__all__`, so that it can be imported directly from the `genshi` package.
Add `Attrs` class to `genshi.core.__all__`, so that it can be imported directly from the `genshi` package.

git-svn-id: 35afe1d183cbd4849519a30d21151995795e8f1d@459 de761a21-4c15-0410-92fa-db90950b6ec0

dag/genshi,dag/genshi,davidfraser/genshi,dag/genshi,davidfraser/genshi,davidfraser/genshi,davidfraser/genshi,dag/genshi