update license and add AUTHORS file. Closes #386

not sure if just saying "Koa contributors" is proper legalese but hey

AUTHORS

@@ -0,0 +1,41 @@
+TJ Holowaychuk <tj@vision-media.ca>
+Jonathan Ong <jonathanrichardong@gmail.com>
+dead_horse <dead_horse@qq.com>
+Julian Gruber <julian@juliangruber.com>
+pana <pana.wang@outlook.com>
+Ian Storm Taylor <ian@ianstormtaylor.com>
+Yiyu He <dead_horse@qq.com>
+Sonny Piers <sonny@fastmail.net>
+yoshuawuyts <i@yoshuawuyts.com>
+fengmk2 <fengmk2@gmail.com>
+PatrickJS <github@gdi2290.com>
+Jan Carlo Viray <virayjancarlo@yahoo.com>
+Jed Schmidt <where@jed.is>
+Johan Bergström <bugs@bergstroem.nu>
+Karl Böhlmark <karl.bohlmark@gmail.com>
+Kenneth Ormandy <kenneth@chloi.io>
+Kim Joar Bekkelund <kjbekkelund@gmail.com>
+Kyle Suss <susskyle@gmail.com>
+Matheus Azzi <matheuslazzi@gmail.com>
+Mathieu Gallé-Tessonneau <mathieu.galletessonneau@gmail.com>
+Matthew Chase Whittemore <matthew@socialtables.com>
+Matthew Mueller <mattmuelle@gmail.com>
+Nathan Rajlich <nathan@tootallnate.net>
+New Now Nohow <empty@cqdr.es>
+Peeyush Kushwaha <peeyush.p97@gmail.com>
+Phillip Alexander <git@phillipalexander.io>
+Qiming zhao <chemzqm@gmail.com>
+Robert Sköld <robert@publicclass.se>
+Ryunosuke SATO <tricknotes.rs@gmail.com>
+Tiago Ribeiro <tlr@seegno.com>
+Tim Schaub <tim.schaub@gmail.com>
+Veselin Todorov <veselin@veselin.bg>
+Yazhong Liu <l900422@vip.qq.com>
+Yoshua Wuyts <yoshuawuyts@gmail.com>
+alsotang <alsotang@gmail.com>
+bhanuc <bhanuc@iitk.ac.in>
+haoxin <coderhaoxin@outlook.com>
+jeromew <jerome.wagner@m4x.org>
+mako-taco <jake.y.scott@gmail.com>
+nicoder <nicolas.dermine@gmail.com>
+superchink <superchink@gmail.com>

LICENSE

@@ -1,6 +1,6 @@
 (The MIT License)
 
-Copyright (c) 2014 TJ Holowaychuk <tj@vision-media.ca>
+Copyright (c) 2015 Koa contributors
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the