Hi Charlie, here's a bug fix and one new feature.

Hey Charlie,
We've used Power Truncate on a number of projects at work and it's been great, however with one minor issue around the returned string length.

### Bug Fix
I've modified Power Truncate (line 42 & 44) to trim the tag data *before* the substring call as this was resulting in (sometimes quite significant) length issues (strings coming out far shorter than they should). If you review this I think you'll see it works as intended now.

This does mean once markup has been replaced that the string can come out longer than the limit, but markup is invisible and doesn't effect the length output on the page.

### New Feature - Markup stripping
When developing EE sites I don't like having a separate intro field for news articles and the likes, but the actual content field is often a WYGWAM field or similar, meaning markup can be output (which I don't always want in a short intro in a sidebar etc). So I added an additional parameter which is used to not replace the markup in the string.


Thanks for creating this plugin and hopefully you'll accept my merge request :)