Changed the type of ESpace to ESpace Double
TeX Renderer: Fixed typo
MathML Reader: Improved behavior of semantic element
MathML Reader: Avoided unecessary grouping

Also ensured that the root element is a math element.
Added EStyled to Exp, implemented in all readers and writers.

EStyled corresponds to mstyle in mathml, and \mathrm, \mathcal, etc.
in LaTeX (which can contain arbitrary math content, not just text).

Note that the Pandoc writer now uses toUnicode to support things
like mathfrak.

Test suite: Split native files before diffing.

Tests not yet updated.

Closes #13.
Merge branch 'master' of https://github.com/mpickering/texmath into mpickering-master

Conflicts:
	src/Text/TeXMath/Readers/MathML.hs
	src/Text/TeXMath/Writers/OMML.hs
	src/Text/TeXMath/Writers/Pandoc.hs