pyandoc with citations, pdf, epub, and pandoc executable from path
added @OiNutter's changes

quoting @OiNutter: "Fix PANDOC_PATH issues: 
I've added a module level method that sets the PANDOC_PATH as using the PANDOC_PATH = 'blah' method wasn't working as described in #5. 
I've also set the default PANDOC_PATH to just pandoc as discussed in #3"
fix indentation
Merge pull request #7 from yoavram/patch-1

pyandoc with citations, pdf, epub, and pandoc executable from path