Update README.md

Fixed OS X StoryIncludes .twee bug

Now, including a local .twee via StoryIncludes will work again in OS X.

HTML <table> cleanup

* Now, HTML <table> structures in passage text will have all invalid
elements removed - that is, non-table-related elements outside of
<tr>,<th>,<col>,<caption> and <figcaption> elements. Note: this doesn't
work in IE 8 simply because inserting HTML <table> elements doesn't work
in IE 8. For maximum compatibility, use the TiddlyWiki table syntax.
* Fixed a syntax highlighter bug where the final trailing symbol of
certain style syntax wasn't being coloured.

OS X story format path tweak

* Jonah: fixed inline image syntax when used in tagged stylesheets.
* Fixed the OS X paths so that the targets folder is now inside the app bundle. Thanks @wolfteeth.
* However, story formats will also be sought in another 'targets' folder placed in the same directory as the app bundle. This allows other formats to be installed.