Given a 3 element RGB vector corresponding to a color (given by the MATLAB color spec http://www.mathworks.com/help/matlab/ref/colorspec.html), return the corresponding hex value string associated with it. This hex value string is often used when coding in HTML to specify a color.

For example, given the vector [0, 1, 1], you would return the string 00FFFF and given the vector [.5 .5 .2], you would return the string 7F7F33. We will assume that in this case once we multiply the vector by 255, we will round down to the nearest integer. If anyone thinks that we should not assume rounding down, feel free to comment :)