Test LaTeX parsing of `\ `
Alias `\space` to `\ `

In addition to being used in various forks of MathQuill (such as
Desmos's), which we'd like to remain back-compat with, it's a real TeX
command that means something pretty similar to `\ `:
http://tex.stackexchange.com/questions/119717/usage-of-latex-macro-space-compared-with