Cleanup Mathjax suite

Just does a bit of cleanup and improve messaging on the MathJax suite:

```
Skipping the following MathJax tests:
 * test/fixtures/MathJax/LaTeXToMathML-tex/above-below/accents-2.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/above-below/buildrel-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/above-below/sideset-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/above-below/subarray-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/arrows/Newextarrow-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/atoms/mathinner-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/atoms/mathop-1a.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/atoms/mathop-1b.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/atoms/mathop-2.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/atoms/mathopenclose-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/atoms/mathord-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/atoms/mathpunct-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/atoms/mathrel-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/basic-operators/backslashed-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/basic-operators/basic-operators-2.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/colors/definecolor-1a.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/colors/definecolor-1b.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/colors/definecolor-1c.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/colors/definecolor-2.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/colors/fcolorbox-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/colors/issue446.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/alignat-1a.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/alignat-1b.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/eqalign-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/eqalignno-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/eqnarray-1a.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/eqnarray-1b.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/eqnarray-1c.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/eqnarray-2a.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/equation-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/equation-2.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/leqalignno-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/multiline-1a.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/environments/multiline-1b.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/frac/cfrac-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/frac/dfrac-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/frac/genfrac-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/kern-1a.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/kern-1b.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/lower-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/mathstrut-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/moveleft-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/moveright-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/newline-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/phantom-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/raise-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/shove-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/skip-1a.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/skip-1b.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/smash-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/spaces-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/strut-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/layout/vcenter-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/matrices/array-2.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/matrices/array-3.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/other/bbox-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/other/displaylines-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/other/enclose-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/other/mathsize-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/other/style-1.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/other/style-2.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/roots/root-2.xtex
 * test/fixtures/MathJax/LaTeXToMathML-tex/roots/root-3.xtex


*** You did 125 and skipped 63: 66.49% coverage ***
```

/cc @arfon