Fixed an issue where there clean method for rango.forms.PageForm.clean() would raise an AttributeError
Added a comment to the code explaining the if block in the clean method and correctly de-indented the return statement.
Merge pull request #1 from canibanoglu/AttrErr-rango.forms.PageForm.clean

AttributeError in rango.forms.PageForm.clean() (thanks to @canibanoglu)