docs: Initial split of README into docs directory

The top-level README document has got pretty unwieldy and so we need to
switch to add some more structure to our documentation. The first step
is to split out sub-sections of the README document into separate files
in a new 'docs' directory.

Whilst splitting up the README, we can also take the opportunity to tidy
things up and fix a couple of typos.

Signed-off-by: Paul Barker <pbarker@toganlabs.com>

docs/contributing.md

@@ -0,0 +1,36 @@
+# Contributing
+
+## Mailing list
+
+The main communication tool we use is a mailing list:
+* yocto@yoctoproject.org
+* https://lists.yoctoproject.org/listinfo/yocto
+
+Feel free to ask any kind of questions but always prepend your email subject
+with "[meta-raspberrypi]". This is because we use the 'yocto' mailing list and
+not a perticular 'meta-raspberrypi' mailing list.
+
+## Patches and pull requests
+
+All the contributions should be compliant with the openembedded patch
+guidelines: http://www.openembedded.org/wiki/Commit_Patch_Message_Guidelines
+
+To contribute to this project you should send pull requests to the github mirror
+(https://github.com/agherzan/meta-raspberrypi). **Additionally** you can send
+the patches for review to the above specified mailing list.
+
+When creating patches for the mailing list, please use something like:
+`git format-patch -s --subject-prefix='meta-raspberrypi][PATCH' origin`
+
+When sending patches to the mailing list, please use something like:
+`git send-email --to yocto@yoctoproject.org <generated patch>`
+
+## Github issues
+
+In order to manage and trace the meta-raspberrypi issues, we use github issues:
+https://github.com/agherzan/meta-raspberrypi/issues
+
+If you push patches which have a github issue associated, please provide the
+issue number in the commit log just before "Signed-off-by" line(s). Example line
+for a bug:
+`[Issue #13]`