Tweak two Rd titles
Staticdocs prefers lower-case .r on linux
remove includeMathJax() and use withMathJax() instead, per suggestion of @jcheng5
Revert "math expressions may come in through renderUI()/uiOutput(), in which case we have to re-typeset the math expressions"

This reverts commit 58471c6971a3e8f90197566b860104f9cf365869.