adding back the license header used by the maven plugin

pom.xml

@@ -42,7 +42,7 @@
         <artifactId>maven-license-plugin</artifactId>
         <version>1.10.b1</version>
         <configuration>
-          <header>license.txt</header>
+          <header>src/license.txt</header>
           <strictCheck>true</strictCheck>
         </configuration>
         <!--executions>

src/license.txt

@@ -0,0 +1,13 @@
+Copyright 2012 Twitter, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.