Move contributing from hacking docs to repo root

A CONTRIBUTING.rst is added to the root of the repo, as Github
automatically recognizes this for incoming PRs
(ref: https://github.com/blog/1184-contributing-guidelines)

Most of the information is directly borrowed from the existing hacking
docs, which is restructured to refer to this file instead for
contribution guidelines

CONTRIBUTING.rst

@@ -0,0 +1,44 @@
+Contributions are welcome & greatly appreciated, every little bit
+helps in making Hy more awesome.
+
+Pull requests are great! We love them, here is a quick guide:
+
+- Fork the repo, create a topic branch for a feature/fix. Avoid
+  making changes directly on the master branch
+
+- All incoming features should be accompanied with tests
+
+- Before you submit a PR, please run the tests and check your code
+  against the style guide.  You can do both these things at once::
+
+    $ make d
+
+- Make commits into logical units, so that it is easier to track &
+  navigate later. Before submitting a PR, try squashing the commits
+  into changesets that are easy to come back to later. Also make sure
+  you don't leave spurious whitespace in the changesets, this avoids
+  creation of whitespace fix commits later.
+
+- As far as commit messages go, try to adhere to
+  the following:
+
+  + Try sticking to the 50 character limit for the first line of git
+    commit messages
+
+  + For more explanations etc. follow this up with a blank line and
+    continue describing the commit in detail
+
+
+- Finally add yourself to the AUTHORS file (as a seperate commit), you
+  deserve it :)
+
+- All incoming changes need to be acked by 2 different members of
+  Hylang's core team. Additional review is clearly welcome, but we need
+  a minimum of 2 signoffs for any change.
+
+- If a core member is sending in a PR, please find 2 core members that doesn't
+  include the PR submitter. The idea here is that one can work with the PR
+  author, and a second acks the entire change set.
+
+- For documentation & other trivial changes, we're good to merge after one
+  ACK. We've got low coverage, so it'd be great to keep that barrier low.

docs/hacking.rst

@@ -89,26 +89,10 @@ To build the docs in HTML::
 Write docs---docs are good! Even this doc!
 
 
-Core Development Rules
-======================
-
-Pull requests are good!
-
-Before you submit a PR, please run the tests and check your code against the style guide.  You can do both these things at once::
-
-    $ make d
-
-All incoming changes need to be acked by 2 different members of Hylang's
-core team. Additional review is clearly welcome, but we need a minimum of
-2 signoffs for any change.
-
-If a core member is sending in a PR, please find 2 core members that don't
-include the PR submitter. The idea here is that one can work with the PR
-author, and a second acks the entire change set.
-
-If the change is adding documentation, feel free to just merge after one
-ACK. We've got low coverage, so it'd be great to keep that barrier low.
+Contributing
+============
 
+.. include:: ../CONTRIBUTING.rst
 
 Core Team
 =========