Unable to use ~ to specify directory

[nabsiddiqui]

This caused some issues when I was testing out PixPlot, and I would have thought there was an error with my installation if I had not downloaded the test files and ran them successfully. The following will not work with PixPlot:

pixplot --images "~/Desktop/images/*" 

While the following does

pixplot --images "pixplot --images "/Users/siddiqui/Desktop/images/*" 

This should be stated somewhere in the readme or altered so that the first also works as it is how OS X, and I believe most Linux installations, will default to.