Gaussian Process for Regression Math Rendering

[smbryan]

@yshi329, some of the formulas in the GP for Regression isn't rendering correctly. Should be a quick fix.

[heethesh]

@smbryan looks like MathJax is not rendering on other articles as well (example)

[heethesh]

PR #81

[smbryan]

@heethesh, your last PR did the trick. Well done.