Restored guessSyntax stub

Eventually we might detect detect the syntax using elements of the
page, which could work better for WordPress blogs (HTML) and forums
(BBCode), as discussed at #3
https://github.com/Cacodaimon/GhostTextForChrome/issues/3#issuecomment-4
7567858
Naming convention as suggested in b204c28. + DOM

+ connectTextArea can also accept normal DOM elements
Restored ES6-like and console.log-like rest parameter. Restored "stay" parameter

No need to use/join arrays
http://ariya.ofilabs.com/2013/03/es6-and-rest-parameter.html