Further improve wording of custom.css file placement
Further improve wording of custom.css file placement

As per: https://github.com/getnikola/nikola/pull/1512#issuecomment-64617067
s2hc-johan/nikola,x1101/nikola,pluser/nikola,xuhdev/nikola,immanetize/nikola,gwax/nikola,gwax/nikola,lucacerone/nikola,getnikola/nikola,xuhdev/nikola,TyberiusPrime/nikola,knowsuchagency/nikola,andredias/nikola,s2hc-johan/nikola,techdragon/nikola,wcmckee/nikola,techdragon/nikola,andredias/nikola,xuhdev/nikola,xuhdev/nikola,okin/nikola,TyberiusPrime/nikola,techdragon/nikola,TyberiusPrime/nikola,okin/nikola,masayuko/nikola,lucacerone/nikola,okin/nikola,knowsuchagency/nikola,JohnTroony/nikola,berezovskyi/nikola,yamila-moreno/nikola,schettino72/nikola,jjconti/nikola,schettino72/nikola,x1101/nikola,masayuko/nikola,lucacerone/nikola,yamila-moreno/nikola,knowsuchagency/nikola,s2hc-johan/nikola,pluser/nikola,andredias/nikola,masayuko/nikola,atiro/nikola,jjconti/nikola,JohnTroony/nikola,atiro/nikola,schettino72/nikola,yamila-moreno/nikola,berezovskyi/nikola,getnikola/nikola,JohnTroony/nikola,jjconti/nikola,atiro/nikola,getnikola/nikola,okin/nikola,wcmckee/nikola,berezovskyi/nikola,wcmckee/nikola,immanetize/nikola,gwax/nikola,x1101/nikola,pluser/nikola,getnikola/nikola,immanetize/nikola