Handle single & double quote

Should fix issue 27

This issue comes when in handlebars you have this kind of thing

```handlebars
{{{sprintf (gettext '<span class="counter">%s</span> foo' '<span class="counter">%s</span> foos' much) much }}}
```

It's a weird case where HTML is included in string to translate because you want another typo or font size for the variable, but have a big long sentences and want to preserve localization, because in some other language the variable can be set in another place in the sentence.

So... double quote in the sentence...

And the hbs extractors transform it to JS like function before calling execution in gettext context

```
gettext("<span class="counter">%s</span> foo", "<span class="counter">%s</span> foos", 0)
```

See how double quote ruins everything.

This PR fixes it by choosing which quote to use, single or double.