Fixed TOC Option parsing.

The new option parser assumes bool values if the default is bool or
None. As the "title" option is not a bool value, it should default to an
empty string rather than None. Fixes #347.
Added a temp workwround for deprecated short ext names.

As we chnaged the order in import trys for short names extensions
(no dot syntax), an extra test was added to the import code for the
occassion when a naming conflict exists. For example, if PyTables
is installed (module name is tables) and the user tries to use
the short name 'tables' instead of 'markdown.extensions.tables'.
Fixes #341.

Of course, this code will get ripped out when the old behavior is
fully deprecated.
Fix the lost tail issue in inlineprocessors.

See #253. Prior to this patch, if any inline processors returned an element
with a tail, the tail would end up empty. This resolves that issue and will
allow for #253 to be fixed. Thanks to @facelessuser for the work on this.
Better nested STRONG EM support.

Fixes #253. Thanks to @facelessuser for the tests. Although I removed
a bunch of weird ones (even some that passed) from his PR (#342). For
the most part, there is no definitive way for those to be parsed. So
there is no point of testing for them. In most of those situations,
authors should be mixing underscores and astericks so it is clear
what is intended.
Run Meta after whitespace normalization

Fixes #343. Thanks for the report @AlexJF.
Upped version to 2.5.1

Also removed an inacurate statement in the 2.5 release notes.
Merge branch 'master' of git://github.com/waylan/Python-Markdown into feature/py26