Replace godep with vndr

Vndr has a simpler configuration and allows pointing to forked
packages. Additionally other docker projects are now using
vndr making vendoring in distribution more consistent.

Updates letsencrypt to use fork.
No longer uses sub-vendored packages.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

vendor/github.com/miekg/dns/rawmsg.go

@@ -0,0 +1,49 @@
+package dns
+
+import "encoding/binary"
+
+// rawSetRdlength sets the rdlength in the header of
+// the RR. The offset 'off' must be positioned at the
+// start of the header of the RR, 'end' must be the
+// end of the RR.
+func rawSetRdlength(msg []byte, off, end int) bool {
+	l := len(msg)
+Loop:
+	for {
+		if off+1 > l {
+			return false
+		}
+		c := int(msg[off])
+		off++
+		switch c & 0xC0 {
+		case 0x00:
+			if c == 0x00 {
+				// End of the domainname
+				break Loop
+			}
+			if off+c > l {
+				return false
+			}
+			off += c
+
+		case 0xC0:
+			// pointer, next byte included, ends domainname
+			off++
+			break Loop
+		}
+	}
+	// The domainname has been seen, we at the start of the fixed part in the header.
+	// Type is 2 bytes, class is 2 bytes, ttl 4 and then 2 bytes for the length.
+	off += 2 + 2 + 4
+	if off+2 > l {
+		return false
+	}
+	//off+1 is the end of the header, 'end' is the end of the rr
+	//so 'end' - 'off+2' is the length of the rdata
+	rdatalen := end - (off + 2)
+	if rdatalen > 0xFFFF {
+		return false
+	}
+	binary.BigEndian.PutUint16(msg[off:], uint16(rdatalen))
+	return true
+}