Added support for multiple header levels. Previously only h3 was allowed.
Added support for multiple header levels. Previously only h3 was allowed.

theerik/pycco,rahuldave/pycco,mhils/pycco,ryanroser/pycco,williamwallacebrave/pycco,gobengo/pycco,hoffmanc/pycco,lincolnloop/pycco,sprin/pycco,rgeoghegan/pycco,pearswj/pycco,ChadFulton/pycco,raylu/pycco,edwelker/pycco,fitzgen/pycco,akaihola/pycco,gorakhargosh/pycco,ryanisnan/pycco,kingcons/pycco,mdornseif/pycco