Fixed an issue with multiple characters appearing after typing one when applying a filter rule more than once

Fixed a bug where the maxLength in Firefox would not use the Autotab default because Firefox defines the maxLength as -1
Added a check to prevent applying filter rules to any input type except text
Added a note to the readme about the minifier that is used in jquery.autotab.min.js
Merge pull request #29 from Mathachew/dev

Fixes for multiple rule definitions and Firefox behavior