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
fix tabbing
Merge pull request #275 from luzfcb/patch-1

Change git submodules to use https instead of git
Merge pull request #276 from fly/fixtabs

fix tabbing
Add language highlighting option to notebook tag

Update documentation and fix small errors
Add tests for notebook tag regex

Update SYNTAX string to match new regex

Explicitly outline necessary order for tag options

Addresses concern in
https://github.com/getpelican/pelican-plugins/pull/283#issuecomment-53731077
Merge pull request #283 from isms/liquid-notebook-language

[liquid_tags:notebook] Add language highlighting option