0.1.2
 - allow strings and lists for `which_data` everywhere (#1)
 - check for valid background keys in image_data.py (#2)
 - add QPImage.info property (#5)
 - add slicing (#6)
 - add references to documentation (#7)
0.1.1
 - QPImage.set_bg_data now accepts QPImage objects
 - add QPSeries for managing multiple QPImages in one hdf5 file (#3) 
0.1.0
 - initial release
