changed the API urls.py so that pages end in '/' a thimble pages can link to their edit page by linking to ./edit -- has as side effect that pages without / are rewritten automatically. Also updated the tests
removed extraneous slash for the editor's /edit link
added testcase for slahs/noslash compatibility
Merge pull request #672 from Pomax/page-as-dir

reference thimble pages as dirs instead of files