Restore doc.go to allow go get to work

Signed-off-by: Yuri Shkuro <ys@uber.com>

Author: Yuri Shkuro

doc.go

@@ -0,0 +1,17 @@
+// Copyright (c) 2017 Uber Technologies, 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.
+
+// Package jaeger contains the code for Jaeger backend.
+// Do not delete this file, it's needed for `go get` to work.
+package jaeger