Added documentation for the PLPythonIntrospectionController class.
Fixed a crash when deleting with the autocomplete table open but no partially typed word.

This scenario occurs when toggling autocomplete using the escape key after deleting all characters in the partial word (thus showing all possible completions at that location). Pressing delete would throw an exception and crash the app because PLAutocompleteViewController tries to delete from its originalInsertion instance variable that is empty in the textView:doCommandBySelector: method. To fix, check if the length of originalInsertion is greater than zero before deleting.
Deleting text now retains the selected entry in the autocomplete table.

In PLAutocompleteViewController textView:doCommandBySelector: method, store the selected completion prior to processing the deleteBackward: selector. After deleting in the superTextView, reselect the row corresponding to the original selected completion in the autocompleteTableView.
Cleanup and minor issue fixed in PLAutocompleteViewController.

Cleaned up variable initializations in updateCompletions. The textView:willChangeSelectionFromCharacterRange:toCharacterRAnge: now properly sets the returned range to NSMakeRange(0, 0), rather than the input range. This issue had no negative effect as the autocompleteTextView was hidden beforehand and its selection set before display.