developer-certificate-of-origin: Add v1.1 from the Linux Foundation

Luis R. Rodriguez [1] has been trying to get information about the
licensing of the Linux kernel's DCO [2] for a while now [3,4], and it
looks like the Linux Foundation just made their view explicit [5,6,7].
This clarifies the copyright and licensing of Linus' two patches:

* 857a183 Update DCO ("signoff") rules to 1.1
* 991bd2e Start documenting the sign-off procedure in SubmittingPatches

From the whois information, developercertificate.org is pretty recent:

  $ whois developercertificate.org
  Domain Name: DEVELOPERCERTIFICATE.ORG
  Domain ID: D170689185-LROR
  Creation Date: 2014-01-15T02:54:55Z
  Updated Date: 2014-01-17T22:11:12Z
  ...
  Name Server: NS2.LINUX-FOUNDATION.ORG
  Name Server: NS1.LINUX-FOUNDATION.ORG

Now that this has an upstream source and it's own license (verbatim
copies only), I'm putting this file in its own branch.  Downloaded
just now:

  $ wget -S -O developer-certificate-of-origin http://developercertificate.org/
  --2014-01-24 15:46:21--  http://developercertificate.org/
  Resolving developercertificate.org... 140.211.169.4
  Connecting to developercertificate.org|140.211.169.4|:80... connected.
  HTTP request sent, awaiting response...
    HTTP/1.1 200 OK
    Server: nginx
    Date: Fri, 24 Jan 2014 23:46:58 GMT
    Content-Type: text/html; charset=UTF-8
    Connection: keep-alive
    Last-Modified: Fri, 17 Jan 2014 23:02:25 GMT
    ETag: "5c188d-6c5-4f0328910e8f0"
    Accept-Ranges: bytes
    Content-Length: 1733
  Length: 1733 (1.7K) [text/html]
  Saving to: ‘developer-certificate-of-origin’

  2014-01-24 15:46:21 (112 MB/s) - ‘developer-certificate-of-origin’ saved [1733/1733]

After which I stripped out the HTML, leaving just the DCO text.

[1]: http://www.do-not-panic.com/
[2]: https://www.kernel.org/doc/Documentation/SubmittingPatches
[3]: http://thread.gmane.org/gmane.linux.kernel/1397613
[4]: http://thread.gmane.org/gmane.linux.kernel/1492612
[5]: http://article.gmane.org/gmane.linux.kernel.wireless.general/118696
[6]: http://article.gmane.org/gmane.linux.kernel/1635433
[7]: http://developercertificate.org/

Signed-off-by: W. Trevor King <wking@tremily.us>
Merge branch 'dco' into contributing-github

* dco:
  developer-certificate-of-origin: Add v1.1 from the Linux Foundation

Signed-off-by: W. Trevor King <wking@tremily.us>
CONTRIBUTING.md: Update SubmittingPatches link

And link to the newly-local DCO.

Signed-off-by: W. Trevor King <wking@tremily.us>
Merge remote-tracking branch 's-o-b/contributing-github'

* s-o-b/contributing-github:
  CONTRIBUTING.md: Update SubmittingPatches link
  developer-certificate-of-origin: Add v1.1 from the Linux Foundation

Signed-off-by: W. Trevor King <wking@tremily.us>