* Improve \sqrt
Make \sqrt out of inline SVGs to ensure a perfect match at the junction between surd and viniculum.
* Tweak for kern clarity
* Fix lint error
* regenerate screenshot tests with sqrts
* Correct advance
Edit the SVG paths so that they have the correct left bearing and advance width values.
This will correct the spacing on the left side of each surd and it will also improve the placment of a root indice.
* Revise scriptstyle surds
In the `main` size, delimiters *do* scale with scriptstyle and scriptscriptstyle.
* update screenshot images containing sqrts
* Use inline SVG for stretchy elements
Replace all background-images with inline SVG code.
Pros:
* `\color` works in all browsers, even IE/Edge
* Better printing
* Much simpler CSS
* No links to background-images
* No `mask`
* No browser-detection
* No external SVG files
* Faster first rendering
Cons
* No image caching
* Heavier HTML load
* Larger JavaScript file
* `\cancel` line is in `px` units, not `em` units
* Remove static/images from make file
* Change \cancel from px to em
* regenerate screenshots for functions using inline svg
