FIX extend function

Following the wiki on [defining extension](/DrPaulBrewer/html5csv/wiki#defining-extensions) I created my first extension (add handsontable for display data) and I found this error: `Uncaught ReferenceError: newFuncs is not defined `

Digging in the code on the `function extend` (line 395) there is a typo: it uses `newFuncs` instead of `newCsvFuncs`.