Wikitextparser

-------
- Fix a bug in detecting nested tables. (21)
- Fix a few bug in detecting tables and template arguments.
- Changed the ``comments`` property of ``Comment`` objects to return an empty list.
- Changed the ``external_links`` property of ``ExternalLink`` objects to return an empty list.

-------
- Fix a bug in setting ``Section.contents`` which only occurred when the title had trailing whitespace.
- Setting ``Section.level`` will not overwrite ``Section.title`` anymore.

-------
* Define ``WikiLink.title`` property. It is similar to ``WikiLink.target`` but will not include the ``fragment``.

-------
- Deprecate using None as the start value of ``__call__``.

-------
- Added fragment property to ``WikiLink`` class (18)
- Added deleter method for ``WikiLink.text`` property.
- Deprecated: Setting ``WikiLink.text`` to ``None``. Use ``del WikiLink.text`` instead.
- Added deleter method for ``WikiLink.target`` property.
- Added deleter method for ``ExternalLink.text`` property.
- Added deleter method for ``Parameter.default`` property.
- Deprecated: Setting ``Parameter.default`` to ``None``. Use ``del Parameter.default`` instead.
- Defined ``WikiText.__call__`` to get a slice of wikitext as string.
- Deprecated ``WikiText.__getitem__``. Use ``WikiText.__call__`` or ``WikiText.string`` instead.

-------
- Fixed a bug in ``Tag.parsed_contents``. (19)