Update opf.jl

Author: odow

perf/opf/opf.jl

@@ -1,3 +1,9 @@
+# Copyright (c) 2017: Miles Lubin and contributors
+# Copyright (c) 2017: Google Inc.
+#
+# Use of this source code is governed by an MIT-style license that can be found
+# in the LICENSE.md file or at https://opensource.org/licenses/MIT.
+
 import Ipopt
 import JuMP
 import MathOptInterface as MOI