[boobot] fix check_twitter method
fix regression introduced by 19a95dc0d6a82e136401b73c12deb0e19b08958f
do not try to parse useless accounts (closes #1432)
raise ParseError only with None/NotAvailable/NotLoaded values, not with empty strings
remove duplicated file
do not crash on months with no transactions
[razibus] add favicon
[boobot/twitter] fix purge system
Add unique id to creditcooperatif (perso)
tests: Use the Python SkipTest if possible

This makes nosetests optional at least in theory.
Recent nose versions already do the same thing internally.
boilerplate: Remove useless __all__
Remove useless __all__ in modules

They bring nothing of value (we never use import * anyway) and introduce
a maintenance burden.

The __all__ that I left might not be very useful either but at least
they are not a pain to maintain; they are also used by pyflakes in some
cases.
Put back wrongly removed __all__
limit length of password
let get_currency guess US$ means USD
add a way to customize sign handling for CleanDecimal
add a way to asynchronously handle requests and pages
ability to set value to an empty string if it is available in choices
[mareeinfo] add new module mareeinfo
require python-concurrent.futures only when needed