mathjax/MathJax-third-party-extensions — pull request #14 by burnpanck (2014-10-12 19:23:35+00:00)
Title: changed optional argument syntax of \img command (img.js extension) to be more LaTeX-like

Optional arguments are now given either as

\img[valign=,width=,height=]{URL}

or

\img[][][]{URL}

which are both common ways to supply optional parameters in LaTeX (the latter is usually used when there is just one optional argument). Example in http://jsfiddle.net/c6sy534g/