Version 2.00

- Refactor the plugin to handle different strategies to preprocess the compared files (used by some advanced filters).
- Offer preprocessing through an externally launched Vim instance, and internally in the current Vim, in addition to the existing external sed tool. Change the default to external Vim, because that offers the fullest feature set, and no need to switch regular expression dialects as with sed. Thanks to Marcelo Montú for suggesting this and sending prototype patches for both external and internal Vim processing!