WIP: Basic config loading works.

This basically works for loading config files. It isn't ideal and I get the following error if I try to load a new config file after loading the first one:

```
---------------------------------------------------------------------------
PyAssertionError                          Traceback (most recent call last)
/home/moorepants/anaconda/lib/python2.7/site-packages/traitsui/wx/file_editor.pyc in show_file_dialog(self, event)
    181             self.popup = self._create_file_popup()
    182         else:
--> 183             dlg       = self._create_file_dialog()
    184             rc        = (dlg.ShowModal() == wx.ID_OK)
    185             file_name = abspath( dlg.GetPath() )

/home/moorepants/anaconda/lib/python2.7/site-packages/traitsui/wx/file_editor.pyc in _create_file_dialog(self)
    261                              style=style)
    262 
--> 263         dlg.SetFilename( self._get_value() )
    264 
    265         return dlg

/home/moorepants/anaconda/lib/python2.7/site-packages/wx-3.0-gtk2/wx/_windows.pyc in SetFilename(*args, **kwargs)
   3163         Sets the default filename.
   3164         """
-> 3165         return _windows_.FileDialog_SetFilename(*args, **kwargs)
   3166 
   3167     def SetWildcard(*args, **kwargs):

PyAssertionError: C++ assertion "volDummy.empty() && pathDummy.empty()" failed at ./src/common/filename.cpp(567) in Assign(): the file name shouldn't contain the path
> /home/moorepants/anaconda/lib/python2.7/site-packages/wx-3.0-gtk2/wx/_windows.py(3165)SetFilename()
   3164         """
-> 3165         return _windows_.FileDialog_SetFilename(*args, **kwargs)
   3166 
```