require YAML where it's needed
require YAML where it's needed

* closes #49

yob/pdf-reader,gordonbisnor/pdf-reader,boutil/pdf-reader,tdenovan/pdf-reader,nmadura/pdf-reader,eitoball/pdf-reader,tardate/pdf-reader,alexdowad/pdf-reader,yob/pdf-reader,yob/pdf-reader,nifarius/pdf-reader