Spellchecking for the message input

[zarino]

Enable spell-checking for outgoing messages: https://github.com/atom/electron/blob/master/docs/api/web-frame.md

Will require an external spellchecking library like http://atom.github.io/node-spellchecker

var webframe = require('web-frame');
var spellchecker = require('spellchecker');

webframe.setSpellCheckProvider("en-US", true, {
  spellCheck: function(text) {
    return ! spellchecker.isMisspelled(text);
  }
});