Improvements to ImageRenderer
 - The resulting image is no longer upside down
 - Land is now transparent
 - The resulting image is no longer 1 to 1 datapoint to pixel, it is resized so that both sides are at least 256 pixels
 - There is a parameter to force the image to be square, even if the rawData is not
Added colors and hardcoded scales for each feature
Merge pull request #6 from stoutbeard/master

Add input validation for salinity resource
Merge pull request #7 from emiljs/master

Improvements to ImageRenderer