Kindle regexes updated

Moved Kindle UA regex below NetFront to properly classify older UAs.
Made sure Kindle Fire is recognized as Android even if it's spoofing
Mac OS X. Moved the Kindle device regexes above Android to avoid
conflicts.
updating the previous kindle test to reflect netfront as the browser
renamed Silk to Amazon Silk
Merge pull request #147 from tobie/kindle

Better support for the Kindle.