Contour plot

My first time contributing to anything (go easy on me :) )

I have provided a ContourPlot class which takes in 3 parameters: 
- data : 2D array of z values
- xrange : array of evenly spaced x points
- yrange : array of evenly spaced y points

The plot creates RGB values based on the value in data and plots it in the rectangle defined by xrange and yrange.

Note: This class requires numpy.