attributions added

[yamanmalkoc]

No description provided.

[jpzg]

We should probably also put their copyright info in the included license files (where there are placeholders in brackets).

[jpzg]

Also: This would close #46.

[jpzg]

On second thought - those placeholders are actually not part of the license, they're in the instructions for how to apply the license to your work:

APPENDIX: How to apply the Apache License to your work.

  To apply the Apache License to your work, attach the following
  boilerplate notice, with the fields enclosed by brackets "[]"
  replaced with your own identifying information.

It's probably not our right or responsibility to add that notice where they did not. So, LGTM.