fully integrate blog and users

previously, users could register and login, but this was not linked to the blog in anyway other than URL. now users must login to post to the blog and each blog post has an author
merge branch 'dev'
Merge branch 'dev'
update sample_app.yaml

update to reflect what my app.yaml looks like after reorganizing my code
simplify verification

Removed unnecessary classes (CookieAuthentication and
UserAuthentication) and added check_login_status() to BaseHandler class
instead. Fixed circular dependancy.