Fixes #776 : use "expires" of simplecookie (of bottle.py)
Be carefull, "expires" uses String and not Datetime nor TimeStamp
see :
http://stackoverflow.com/questions/7913169/python-bottle-persistent-cookie-not-working
Use persistent cookies by defaut
Merge pull request #786 from DessaiImrane/fix-776

Fixes #776 : use "expires" of simplecookie (of bottle.py)