changed git  submodule config to use https instead of git

changed git  submodule config to use https instead of git
git on submodule result in erros

see: https://travis-ci.org/pythonclub/pythonclub.github.io
Merge pull request #275 from luzfcb/patch-1

Change git submodules to use https instead of git
added pelican-langcategory plugin