Select result when wrapping with parentheses

The first commit simply wraps CodeMirror's option for controlling where the cursor goes after replacing text.

The second uses this behaviour so that after selecting text and wrapping it in parentheses, the resulting expression will be selected. This mirrors the behaviour of Sublime Text / Atom etc., and IMO is much nicer since you usually want to go to the start of the expression and add a function call.

The third fixes an issue with paren removing, which previously behaved strangely when there was a selection finishing on a bracket.