Copyright information is not available for some files

Goamz is a dependency for juju-core.
Due to a nature of golang applications (static linking of all the deps) we have to include goamz source code into the juju-core source package.
While working on debian/copyright file for juju-core I figured out that some of goamz's files don't have appropriate copyright information.
W/o copyright and license information we can't redistribute this code.

We have two ways to fix the issue:
(1) add 'default' copyright notice to the LICENSE file; it will be applied to all files w/o copyright
(2) add copyright notice to all the files which lack it
Way #1 looks much simpler to me.

Please note that you may update just upstream files and I'll put a reference to this commit to d/copyright.

Thanks for helping!

License file to update: https://github.com/go-amz/amz/blob/v1/LICENSE

Files w/o copyright information:

iam/iamt_test.go
iam/sign.go
iam/iami_test.go
iam/iam_test.go
iam/responses_test.go
iam/iamtest/server.go
iam/iam.go
testutil/suite.go
testutil/http.go
ec2/ec2i_test.go
ec2/ec2t_test.go
ec2/responses_test.go
ec2/export_test.go
ec2/ec2_test.go
ec2/ec2test/server.go
ec2/ec2test/filter.go
aws/sign_test.go
aws/sign.go
aws/attempt_test.go
aws/aws_test.go
aws/attempt.go
s3/s3i_test.go
s3/sign_test.go
s3/sign.go
s3/s3_test.go
s3/multi_test.go
s3/s3test/server.go
s3/responses_test.go
s3/multi.go
s3/export_test.go
s3/s3t_test.go
exp/sdb/sign_test.go
exp/sdb/sign.go
exp/sdb/responses_test.go
exp/sdb/export_test.go
exp/sdb/sdb_test.go
exp/sns/sign.go
exp/sns/Makefile
exp/sns/README
exp/sns/responses_test.go
exp/sns/sns_test.go
exp/mturk/sign_test.go
exp/mturk/sign.go
exp/mturk/responses_test.go
exp/mturk/export_test.go
exp/mturk/mturk_test.go