Merge branch 'feature/#28_openfilefilters' into develop

CHANGES.txt

requirements.txt

site-packages/pyqtgraph/.coveragerc

site-packages/pyqtgraph/.gitignore

site-packages/pyqtgraph/.mailmap

site-packages/pyqtgraph/.travis.yml

site-packages/pyqtgraph/CHANGELOG

site-packages/pyqtgraph/CONTRIBUTING.txt

site-packages/pyqtgraph/LICENSE.txt

site-packages/pyqtgraph/MANIFEST.in

site-packages/pyqtgraph/README.md

site-packages/pyqtgraph/doc/Makefile

site-packages/pyqtgraph/doc/extensions/qt_doc.py

site-packages/pyqtgraph/doc/listmissing.py

site-packages/pyqtgraph/doc/make.bat

site-packages/pyqtgraph/doc/source/3dgraphics.rst

site-packages/pyqtgraph/doc/source/3dgraphics/glaxisitem.rst

...ckages/pyqtgraph/doc/source/3dgraphics/glgraphicsitem.rst

site-packages/pyqtgraph/doc/source/3dgraphics/glgriditem.rst

...-packages/pyqtgraph/doc/source/3dgraphics/glimageitem.rst