Removed `--latexmathml`, `--gladtex`, `--mimetex`, `--jsmath`, `-m`,
`--asciimathml` options.
Removed `JsMath`, `LaTeXMathML`, and `GladTeX` constructors from
`Text.Pandoc.Options.HTMLMathMethod` [API change].
Removed unneeded data file LaTeXMathML.js and updated tests.
Bumped version to 2.2.