Fix bug in RCData parsing.
Fix bug in RCData parsing.

* We weren't correctly switching the insertion mode to text. This resulted in
  incorrectly handling data state switching during the rcdata parsing.

dushmis/go-html-transform,webfd/go-html-transform,lambdaX/go-html-transform,d0f/go-html-transform,wangcheng711/go-html-transform,x140cc/go-html-transform