Add license header

Author: theotherjimmy

tools/targets/lint.py

@@ -1,11 +1,26 @@
 """A linting utility for targets.json
 
 This linting utility may be called as follows:
-python <path-to>/lint.py TARGET [TARGET ...]
+python <path-to>/lint.py targets TARGET [TARGET ...]
 
 all targets will be linted
 """
 
+# mbed SDK
+# Copyright (c) 2017 ARM Limited
+#
+# 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.
+
 from os.path import join, abspath, dirname
 if __name__ == "__main__":
     import sys