Add GitHub README
Fix readme location, improve WP Repo listing.
Disable dialog caching and fix validation display

Shortcode creator dialog box has a URL form field.  Modern browsers
won't let the form be submitted with an invalid URL. However, the URL
field could be hidden behind a jQuery UI accordion, thus hiding
validation errors.

Solution was to open all accordion sections before submitting form.
Add some reset CSS styles for tweet box
CSS layout improvements
Add other plugins by John box to dashboard.