vendor: revendor github.com/opencontainers/image-tools@da84dc9dddc823a32f543e60323f841d12429c51

This requires re-vendoring a bunch of other things (as well as the old
Sirupsen/logrus path), the relevant commits being:

* github.com/xeipuuv/gojsonschema@0c8571ac0ce161a5feb57375a9cdf148c98c0f70
* github.com/xeipuuv/gojsonpointer@6fe8760cad3569743d51ddbb243b26f8456742dc
* github.com/xeipuuv/gojsonreference@e02fc20de94c78484cd5ffb007f8af96be030a45
* go4.org@034d17a462f7b2dcd1a4a73553ec5357ff6e6c6e

Signed-off-by: Aleksa Sarai <asarai@suse.de>

vendor/github.com/opencontainers/image-spec/schema/doc.go

@@ -0,0 +1,16 @@
+// Copyright 2016 The Linux Foundation
+//
+// 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 schema defines the OCI image media types, schema definitions and validation functions.
+package schema