Update pdfquery to accept new versions of PDFMiner

Since this commmit: https://github.com/euske/pdfminer/commit/2221163b944d2fd28b9a46a6b73d049a533d009e

PDFDocument is located on pdfdocument.py, not more on pdfparser.py
Update requires.txt
Maintain pdfquery compatible with newer and older versions of PDFMiner
Reverts commit fa399e25379fbe6002bbb939e5e56265901a1a0d
Merge pull request #9 from gmorada/master

Fix import for newer versions of PDFMiner.