Added a couple of settings to allow phantomjs to attempt to render images at lower quality if the output PNG size exceeds a specified limit.  Added: max_size - an optional value (in bytes) that will cause a re-try of the render at progressively lower quality until the max_size limit is satisfied.  Added: min_quality - an integer value that will provide a lower bound to the attempts at shrinking the PNG size.  Added: quality_increment - an integer value representing the quality increment to descend as the program attempts to satisfy the max_size limit. Default is 5.   Added: render_timeout - allows user to specify the milliseconds to wait before rendering the page. Default is 200.