Edited the mix function to create a pixel made of two materials.

Modified the mix function to create a pixel that is either constrained or unconstrained in it's mixture.
Edited the get_image function.

Changed the function round the values that it was creating for the pixel_values.
Edited the sensordesign.py file.

Inside of the test_data added the constrained= false argument.
Merge pull request #1 from wc351/development

Development