Users/Orgs for Quick Panel should also be an array of strings

Having something like this (in plugin settings): `"include_orgs": ["wat"]`
I've got this error:
```
Traceback (most recent call last):
  File "Library/Application Support/Sublime Text 3/Packages/Gist/gist.py", line 103, in _fn
    return fn(*args, **kwargs)
  File "Library/Application Support/Sublime Text 3/Packages/Gist/gist.py", line 638, in run
    self.get_window().show_quick_panel(gist_names, on_gist_num)
  File "/Applications/Sublime Text.app/Contents/MacOS/sublime.py", line 355, in show_quick_panel
    items_per_row, on_select, on_highlight, flags, selected_index)
TypeError: String required
error: Gist: unknown error (please, report a bug!)
```
This PR solves this issue by suppling org/users as an array of string - like other gists are.