Update CONTRIBUTING.

 - Mention that we accept patches via GitHub, but keep the mailing
   list address for the few people who prefer those.
 - Remove git send-email instructions; those who want to send patches
   via email already know how to do it, and the rest will just get
   confused.
 - Rename to CONTRIBUTING.md because this file already contained
   only Markdown markup.

Author: whitequark

CONTRIBUTING.md

@@ -0,0 +1,34 @@
+# Sending Patches
+
+Patches for MiSoC may be sent via GitHub pull requests. Alternatively, if
+you prefer using mailing lists, they can also be sent to the public mailing
+list <[email protected]> after subscribing at 
+https://ssl.serverraum.org/lists/listinfo/devel.
+
+Before sending patches, please read the rest of this guide and make sure your
+patch meets the following criteria;
+
+ - [ ] Meets style guide requirements listed below.
+ - [ ] Includes a suitable commit message.
+
+## Help
+
+If your submission is large and complex and/or you are not sure how to proceed,
+feel free to discuss it on the mailing list or IRC (#m-labs on Freenode)
+beforehand.
+
+## Style Guide
+
+All code should be compliant with the
+[PEP8 style guide](https://www.python.org/dev/peps/pep-0008/).
+
+You can use the [pep8 tool](https://www.python.org/dev/peps/pep-0008/) to check
+compliance with `pep8 myfile.py`
+
+When modifying existing code **be consistent** with any existing code style.
+
+# License
+
+All new contributions should be under the same license as MiSoC. This is a very
+permissive two-clause BSD license. Full license text can be found at
+https://github.com/m-labs/misoc/blob/master/LICENSE