Fixed pre-existing bug breaking use of ReST-style syntax in Markdown when specifying a Gist ID without a file-name, added doctest to cover this case.
Fixed pre-existing bug breaking use of ReST-style syntax in Markdown when specifying a Gist ID without a file-name, added doctest to cover this case.

masayuko/nikola,pluser/nikola,immanetize/nikola,getnikola/nikola,yamila-moreno/nikola,okin/nikola,masayuko/nikola,schettino72/nikola,berezovskyi/nikola,s2hc-johan/nikola,xuhdev/nikola,techdragon/nikola,berezovskyi/nikola,x1101/nikola,knowsuchagency/nikola,lucacerone/nikola,wcmckee/nikola,schettino72/nikola,s2hc-johan/nikola,gwax/nikola,JohnTroony/nikola,masayuko/nikola,immanetize/nikola,TyberiusPrime/nikola,atiro/nikola,atiro/nikola,jjconti/nikola,JohnTroony/nikola,techdragon/nikola,wcmckee/nikola,yamila-moreno/nikola,TyberiusPrime/nikola,techdragon/nikola,getnikola/nikola,s2hc-johan/nikola,wcmckee/nikola,andredias/nikola,TyberiusPrime/nikola,okin/nikola,gwax/nikola,andredias/nikola,jjconti/nikola,xuhdev/nikola,pluser/nikola,getnikola/nikola,pluser/nikola,xuhdev/nikola,schettino72/nikola,jjconti/nikola,lucacerone/nikola,knowsuchagency/nikola,lucacerone/nikola,x1101/nikola,yamila-moreno/nikola,okin/nikola,x1101/nikola,atiro/nikola,andredias/nikola,knowsuchagency/nikola,getnikola/nikola,xuhdev/nikola,gwax/nikola,immanetize/nikola,JohnTroony/nikola,okin/nikola,berezovskyi/nikola