implements HTTP Basic Auth and fixes issue #4.

Update AUTHORS

Basic auth decorator

This is much less flexible than .login_required() (because HTTP
authentication is less flexible than custom login pages), but easier to
use in a simple proof-of-concept.

Now .login_required() and .group_required() document what they require
LDAP_LOGIN_VIEW to do.

Fixes #3.

to link to the new example using blueprints and app factories

Use a python code block for syntax rendering

Re-added flask themes, seems to work now ..