make lib/pdf2jpg.js for convert a pdf file to jpg files.

this file uses imagemagick.js.
please try:
 $ npm install imagemagick
fix pdf2jpg.js and add info of dependencies in package,json.

usage of pdf2jpg:
  require('pdf2jpg').convert(targetFile, function(err, convertedFile){
      console.log(err, convertedFile);
  })
Merge https://github.com/nazomikan/SlideNote into trunk

Conflicts:
	package.json
Merge pull request #1 from otakky/trunk

make lib/pdf2jpg.js for convert a pdf file to jpg files.