Make wrapCharacters -> escapeString. Use a regex.

The `htmlForScreenRows` benchmark went from ~3.5 ms to ~2.9ms for a 
call to htmlForScreenRows over the entire screen range.

🐎

benchmark/benchmark-suite.coffee

@@ -95,7 +95,7 @@ describe "editor.", ->
       benchmark "resetDisplay", 50, ->
         editor.resetDisplay()
 
-      benchmark "htmlForScreenRows", 50, ->
+      benchmark "htmlForScreenRows", 1000, ->
         lastRow = editor.getLastScreenRow()
         editor.htmlForScreenRows(0, lastRow)