CONTRIBUTING.md: Add github style contributing rules

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

CONTRIBUTING.md

@@ -0,0 +1,89 @@
+Contributing to libmraa                           {#contributing}
+======================
+
+libmraa is an opensource project and we are actively looking for people to help
+with:
+
+- Writing platform supports for all types of boards running linux
+- People to extend the functionality, API with useful functions
+- Anything we haven't thought about :) Ideas always welcome!
+
+The recommended method to contribute is to fork on github, and then send pull
+requests to the main project. You can open issues if you find any bugs/have
+questions.
+
+If you'd rather not use github you are more than welcome to send git formatted
+patches to brendan.le.foll@intel.com.
+
+Basic rules
+-----------
+- Your code must build
+- Commits must have a sign-off line by at least yourself
+- Commits must be named <file/module>: Some decent description
+- Try not to break master. In any commit.
+- Try to split commits up logically, you will be asked to rebase them if they
+  are not.
+- Try to stick to the established coding style regardless of your personal
+  feeling for it! Use clang-format (3.6+ required)
+
+Coding Style
+------------
+
+Coding style for all code is defined by clang-format, have a look at it. Avoid
+styling fixes as they make history difficult to read. Javascript & Java can
+also be parsed through the clang-format, it complains but seems to do an ok
+job. Few exceptions to coding styles:
+- All python code is indented by 2 spaces
+- CmakeLists files are 2 space indented and a space is required before all
+  brackets so endif () and if () and command (). Also use lowercase for
+  everything but variables. Cmake is case insensitive but this isn't the wild
+  wild west ;-)
+
+Use common sense and don't be afraid to challenge something if it doesn't make sense!
+
+Code signing
+------------
+
+The sign-off is a simple line at the end of the explanation for the
+patch, which certifies that you wrote it or otherwise have the right to pass it
+on as an open-source patch.  The rules are pretty simple: if you can certify
+the below:
+
+        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.
+
+then you just add a line saying
+
+	Signed-off-by: Random J Developer <random@developer.example.org>
+
+Using your real name (sorry, no pseudonyms or anonymous contributions.)
+
+Where to find us
+----------------
+
+Hop onto the freenode network on IRC and join #mraa. Please be patient as we're
+not always online.
+