Added sign in and registration using SQLAlchemy and Flask-User

(Using pre-existing templates)

Also got rid of /patients for now, since that can just be /
It also says you can do it in the case of bulky with statements and assertions. I think the more general rule here is "parens for expressions, backslash for statements". And, if you have a choice between breaking up a statement or one of its subexpressions, go for the expression.