`godep save` results in incomplete dependency list

Steps to reproduce:

    go get github.com/crowdmob/goamz/sqs
    godep save

This results in the following dependency:

    github.com/crowdmob/goamz/aws

... which is incorrect. The `sqs` directory depends on the `aws` directory, but because the `aws` is first alphabetically and in the same git repo, the `sqs` directory is ignored. This change is probably overkill, since it adds multiple dependencies per git repo, but it at least makes `godep save` work. I'm happy to hear feedback on this PR!