fixed a keyerror when passing a list into setBrush

- https://groups.google.com/forum/#!topic/pyqtgraph/xVyCC2f7gVo

Signed-off-by: Nicholas Tan Jerome <nicholas.jerome@kit.edu>
added "mask" key check on setPen as well

Signed-off-by: Nicholas Tan Jerome <nicholas.jerome@kit.edu>
Merge remote-tracking branch 'nicolaisi/brush' into scatterplot-fix
Added unit tests
Merge branch 'scatterplot-fix' into develop