traying to fix travis.yml... again

fix travis.yml

trying to remove preparation for pep8 check

add unit test for login failure

fix service unavailable template

adding unit tests for demo backend

better exceptions handling for demo backend

fix pep8

better unit tests on authentication

cleaner way to merge user's attributes from different backends

fix decorator handling the exceptions

slightly cleaner way to handle templates loading

pep8 compliance

small code reorganization ...

* extraction of exception decorator
* extraction of log handling

Update README.rst

increment version number in doc

increment version number

fill ChangeLog

using demo backend as an example ...

the demo backend is far simplier than the ldap backend,
so it's more logic to use it as an implementation example

adding documentation for demo

adding a demo backend

adding documentation for custom js

implementing custom js

better comment in default configuration + add section ...

* better comments in default config about static file serving
* adding section for futur functionality: adding custom js files
  (for auto-fill)

cosmetic change in doc

complete AD backend documentation

adding confirqtion for backends

typo in changelog

ChangeLog at root of repo + log of current devs.

fix some typos