Shortcodes are case sensitive

[pospiech]

I have used an other plugin that uses [TOC].
I switches to your plugin, however non of the shortcodes are recognised.
I need to rewrite them to [toc]

I conside this as a bug, since shortcodes should not be case sensitive.
Therefore I would aapreciate it if the next minor release would work with upper case shortcodes as well.