Extracted from a production application I co-authored, BBDecode will take a
string of BBCode and parse it into its XHTML representation::
    >>> from bbdecode import bbdecode
    >>> bbdecode('[b]Hello[/b]')

BBDecode attempts to emit valid XHTML even from improperly nested BBCode
input or input with unclosed tags, and does a fair job of it::

    >>> bbdecode('[b]Bold [i]Bold Italic[/b]')
    <b>Bold <i>Bold Italic</i></b>


The current implementation contains handlers for a common subset of tags
found on most forum softwares, with some additional features like more
optional arguments.

In addition to the normal argument supplied to some bbcode tags in many bbcode
dialects (such as in `[quote="Author"]`) bbdecode can take optional arguments
in an HTML-style key=value form, and can take either quoted or unquoted
strings.  For example:: 

    `[img width=28 height="40"][/img]

BBDecode is theoretically unicode-friendly, but this remains to be seen once
things are tested.


The future of this project is to add some more useful tags, and make the
ability to add/remove/customize the available tags so that this library can
be used in support of other forums

In addition, while BBDecode currently requires pyparsing, it may be switched
to another parser like TPG or a custom parser in the future.

The parser is currently recursive descent and emits output directly to the
stream, whether it will in the future build an intermediate parse tree I am
not sure. Recursive descent parsing can be abused by users who just
continuously nest tags to break the parser by causing a stack overflow, this
could be mitigated by setting max depths in the parser.