Clarify license as MIT.

Include a LICENSE file, giving original work copyright to Andy Smith, and modifications by Gary Jones.

LICENSE

@@ -0,0 +1,20 @@
+Original work Copyright (c) 2007 Andy Smith
+Modified work Copyright (c) 2012 Gary Jones
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

composer.json

@@ -4,7 +4,7 @@
     "type": "library",
 	"keywords": ["oauth"],
 	"homepage": "https://github.com/GaryJones/OAuth",
-	"license": "BSD-3-Clause",
+	"license": "MIT",
     "authors": [
         {
             "name": "Gary Jones",