Feature request: Case-insensitive versions of tk/stk/literal?

[ethindp]

I'm writing a parser for a case-insensitive language. Though I could just enumerate all possible permutations of keywords, this seems like it'd create code smell more than anything else. (I could also just do .map(x => ...), but again, this seems like unnecessary bloat.) Please add case-insensitive versions of tk/stk/literal.