Ignore empty cookie keys

[yanigisawa]

Without this check for the 'key' variable, there is an empty key in the resulting dictionary, e.g:

{ 
   'first': u'IamTheFirst', 
   'a': u'2', 
   'second': u'andMeTwo', 
   '': '' 
}

closes #1245

[lepture]

Manually triggered re-build. There is a style error, please fix it by validating with flake8.

[yanigisawa]

Flake8 issue resolved