Allow additional arguments to be passed into hooks

If a packager wants to be able to support addititional arguments on his
hook this will allow them to setup the configuration with these arguments.

For example this would allow a hook developer to add support for a --debug
flag to change the level of debugging in his hook.

In order to complete this task, I had to vendor in the latest
github.com://opencontainers/runtime-tools, which caused me to have to fix a
Mount and Capability interface calls

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

vendor/github.com/xeipuuv/gojsonschema/schemaReferencePool.go

@@ -0,0 +1,68 @@
+// Copyright 2015 xeipuuv ( https://github.com/xeipuuv )
+//
+// 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.
+
+// author           xeipuuv
+// author-github    https://github.com/xeipuuv
+// author-mail      xeipuuv@gmail.com
+//
+// repository-name  gojsonschema
+// repository-desc  An implementation of JSON Schema, based on IETF's draft v4 - Go language.
+//
+// description      Pool of referenced schemas.
+//
+// created          25-06-2013
+
+package gojsonschema
+
+import (
+	"fmt"
+)
+
+type schemaReferencePool struct {
+	documents map[string]*subSchema
+}
+
+func newSchemaReferencePool() *schemaReferencePool {
+
+	p := &schemaReferencePool{}
+	p.documents = make(map[string]*subSchema)
+
+	return p
+}
+
+func (p *schemaReferencePool) Get(ref string) (r *subSchema, o bool) {
+
+	if internalLogEnabled {
+		internalLog(fmt.Sprintf("Schema Reference ( %s )", ref))
+	}
+
+	if sch, ok := p.documents[ref]; ok {
+		if internalLogEnabled {
+			internalLog(fmt.Sprintf(" From pool"))
+		}
+		return sch, true
+	}
+
+	return nil, false
+}
+
+func (p *schemaReferencePool) Add(ref string, sch *subSchema) {
+
+	if internalLogEnabled {
+		internalLog(fmt.Sprintf("Add Schema Reference %s to pool", ref))
+	}
+	if _, ok := p.documents[ref]; !ok {
+		p.documents[ref] = sch
+	}
+}