Update Contributors

New on rails3:
+* Aaron Stone <aaron@serendipity.cx>
+* Filip Hrbek <filip.hrbek@gmail.com>
+* Glenn Poston <gposton1040@gmail.com>
+* Jeff Weiss <jeff.weiss@puppetlabs.com>
+* Karel Brezina <karel.brezina@gmail.com>

Import from master:
+* Zachary Adam Kaplan <razic@viralkitty.com>