Remove CONTRIBUTING

Repo doesn't get enough contributions and the CONTRIBUTING file was rather
bloated anyway.

CONTRIBUTING.md

@@ -1,29 +0,0 @@
-CONTRIBUTING
-============
-
-If you have any kind of feedback, simply create an issue on Github. This makes
-it easier for everyone to track and comment recent developments.
-
-If you want to contribute, please keep a few simple rules in mind:
-
-#### The commit
-
-- One commit per fix/addition.
-- The short commit message shouldn't be longer than 50 characters.
-- The short commit message must start with an uppercase character.
-- The short commit message must start with the affected section or file followed
-  by a colon.
-- The short commit message must use the
-  [imperative](https://en.wikipedia.org/wiki/Imperative_mood).
-- The short commit message mustn't end with a `.`.
-- The short commit message can be simply "Grammar" or "Typo", if the patch
-  fixes, well, grammar or typos.
-- It's always a good idea to have a look at other commits to get an idea how to
-  format one's own commits messages.
-
-#### Example
-
-```
-Bad:  "added my new plugin"
-Good: "Plugins: add vim-newplugin"
-```