Add developer certificate of origin instructions

Merge pull request #19 from wphicks/fea-dco

Taken from https://github.com/NVIDIA/TensorRT/blob/master/CONTRIBUTING.md

CONTRIBUTING.md

@@ -27,6 +27,43 @@ To contribute code to this project, please follow these steps:
 6. Wait for other developers to review your code and update your PR as needed.
 7. Once a PR is approved, it will be merged into the main branch.
 
+#### Signing Your Work
+* We require that all contributors "sign-off" on their commits. This certifies that the contribution is your original work, or you have rights to submit it under the same license, or a compatible license.
+  * Any contribution which contains commits that are not Signed-Off will not be accepted.
+* To sign off on a commit you simply use the `--signoff` (or `-s`) option when committing your changes:
+  ```bash
+  $ git commit -s -m "Add cool feature."
+  ```
+  This will append the following to your commit message:
+  ```
+  Signed-off-by: Your Name <[email protected]>
+  ```
+* Full text of the DCO:
+  ```
+    Developer Certificate of Origin
+    Version 1.1
+    
+    Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+    1 Letterman Drive
+    Suite D4700
+    San Francisco, CA, 94129
+    
+    Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
+  ```
+  ```
+    Developer's Certificate of Origin 1.1
+    
+    By making a contribution to this project, I certify that:
+    
+    (a) The contribution was created in whole or in part by me and I have the right to submit it under the open source license indicated in the file; or
+    
+    (b) The contribution is based upon previous work that, to the best of my knowledge, is covered under an appropriate open source license and I have the right under that license to submit that work with modifications, whether created in whole or in part by me, under the same open source license (unless I am permitted to submit under a different license), as indicated in the file; or
+    
+    (c) The contribution was provided directly to me by some other person who certified (a), (b) or (c) and I have not modified it.
+    
+    (d) I understand and agree that this project and the contribution are public and that a record of the contribution (including all personal information I submit with it, including my sign-off) is maintained indefinitely and may be redistributed consistent with this project or the open source license(s) involved.
+  ```
+
 ## Implementation Details
 
 ### Triton Classes