Documentation updates.
- only visit each objid once when dumping all objects
Added: -R option.
Fix for malformed PDFs.
Changed / to // for clarity.
Fix PDFBox hyperlink.
Merge pull request #40 from meisterluk/master

Fix PDFBox hyperlink.
Added the description of boxes_flow.
Fixed the PNG predictor bug. Thanks to Gabor Molnar.
Applied a patch by Axel Kaiser.
Applied a patch by Axel Kaiser.
Fixed dumppdf.py issues.
Code cleanup.
Documentation updated.
Version 20140324
Fixed: issues #45
Version 20140327
Revert the wrong fix.
Fixed: PDFXRefStream.get_objids returns invalid objids.
Cleanup: isinstance