drop pdfjs parser in favor of HummusJS

[bjrmatos]

drop pdfjs parser in favor of HummusJS

[bjrmatos]

hummujs is a native dependency so if we choose to use as a electron-html-to dependency it will require the user to re-compile the module using something like electron-rebuild, probably a PITA so for now i'll try to not do this change. hopefully the pdfjs parser would be extracted and nothing of this will be required