Use set instead of list for Plane's internal collection of objects.
Optimize group_textboxes function.
pdfminer.cmap python package does not exists
Merge remote-tracking branch 'dangra/master'
Merge remote-tracking branch 'jcushman/patch-2'
Merge remote-tracking branch 'jcushman/patch-1'
resolve all attributes on a page
simplify `isinstance()` check
correct PNG parsing
version bump
Merge remote-tracking branch 'matchbox/master'

Conflicts:
	pdfminer/layout.py
bump version number