diff --git a/vendor/github.com/gogo/protobuf/proto/duration.go b/vendor/github.com/gogo/protobuf/proto/duration.go
new file mode 100644
index 0000000..93464c9
--- /dev/null
+++ b/vendor/github.com/gogo/protobuf/proto/duration.go
@@ -0,0 +1,100 @@
+// Go support for Protocol Buffers - Google's data interchange format
+//
+// Copyright 2016 The Go Authors.  All rights reserved.
+// https://github.com/golang/protobuf
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package proto
+
+// This file implements conversions between google.protobuf.Duration
+// and time.Duration.
+
+import (
+	"errors"
+	"fmt"
+	"time"
+)
+
+const (
+	// Range of a Duration in seconds, as specified in
+	// google/protobuf/duration.proto. This is about 10,000 years in seconds.
+	maxSeconds = int64(10000 * 365.25 * 24 * 60 * 60)
+	minSeconds = -maxSeconds
+)
+
+// validateDuration determines whether the Duration is valid according to the
+// definition in google/protobuf/duration.proto. A valid Duration
+// may still be too large to fit into a time.Duration (the range of Duration
+// is about 10,000 years, and the range of time.Duration is about 290).
+func validateDuration(d *duration) error {
+	if d == nil {
+		return errors.New("duration: nil Duration")
+	}
+	if d.Seconds < minSeconds || d.Seconds > maxSeconds {
+		return fmt.Errorf("duration: %#v: seconds out of range", d)
+	}
+	if d.Nanos <= -1e9 || d.Nanos >= 1e9 {
+		return fmt.Errorf("duration: %#v: nanos out of range", d)
+	}
+	// Seconds and Nanos must have the same sign, unless d.Nanos is zero.
+	if (d.Seconds < 0 && d.Nanos > 0) || (d.Seconds > 0 && d.Nanos < 0) {
+		return fmt.Errorf("duration: %#v: seconds and nanos have different signs", d)
+	}
+	return nil
+}
+
+// DurationFromProto converts a Duration to a time.Duration. DurationFromProto
+// returns an error if the Duration is invalid or is too large to be
+// represented in a time.Duration.
+func durationFromProto(p *duration) (time.Duration, error) {
+	if err := validateDuration(p); err != nil {
+		return 0, err
+	}
+	d := time.Duration(p.Seconds) * time.Second
+	if int64(d/time.Second) != p.Seconds {
+		return 0, fmt.Errorf("duration: %#v is out of range for time.Duration", p)
+	}
+	if p.Nanos != 0 {
+		d += time.Duration(p.Nanos)
+		if (d < 0) != (p.Nanos < 0) {
+			return 0, fmt.Errorf("duration: %#v is out of range for time.Duration", p)
+		}
+	}
+	return d, nil
+}
+
+// DurationProto converts a time.Duration to a Duration.
+func durationProto(d time.Duration) *duration {
+	nanos := d.Nanoseconds()
+	secs := nanos / 1e9
+	nanos -= secs * 1e9
+	return &duration{
+		Seconds: secs,
+		Nanos:   int32(nanos),
+	}
+}