Fix Broken Tests
In preparation for adding new tests, let's fix the existing ones.
3 Unit tests and one Functional test still fail.

* Two unit tests are bugs in xhtmldiff
* One is a bug in Maruku
* A file upload functional test fails, for reasons that escape me.

test/fixtures/webs.yml

test/functional/wiki_controller_test.rb

test/unit/page_renderer_test.rb

test/unit/web_test.rb