Responsive Image Grid with Different Heights and Widths

I need to be able to create a responsive image grid with different image widths, (link to an image below.)

http://ift.tt/1LIWzr0

Here's what I have right now.

http://ift.tt/1RSTUd1

This ^ fits and looks good on my 27" iMac, but isn't responsive, and I haven't been able to figure out a good solution for it due to the varying heights and widths. Masonry.js didn't work for me as I'm developing this site in Wordpress and the grid is created dynamically. I need to know if there is another option for this. Thanks to all in advance!