Allows entering multiple consecutive spaces

The behaviour has been changed to allow multiple consecutive spaces to be entered, they are only removed when .getContent() is called (when the content is saved to the server). This also allows spaces to be entered into new paragraphs.

Note: This could be a breaking change for some people.
```javascript
var nonWhiteSpaceCharacters = [' ', '\x20', '\xa0'].reduce(function(acc, value) {
  if (value.replace(/\s/g, '') !== '') {
    acc.push(value);
  }
  return acc;
}, []);
console.log(nonWhiteSpaceCharacters);
// []
```