Add CONTRIBUTING.md

.gitignore

@@ -6,5 +6,6 @@
 !doc/startify.txt
 !plugin/startify.vim
 !README.md
+!CONTRIBUTING.md
 !syntax/startify.vim
 !startify.png

CONTRIBUTING.md

@@ -0,0 +1,22 @@
+CONTRIBUTING
+============
+
+If you intend to contribute to this project, please keep some simple rules in
+mind:
+
+    - the short commit message shouldn't be longer than 50 characters
+    - the short commit message should start with an uppercase character
+    - use the imperative for the short commit message
+    - don't use github-specific syntax to close an issue (I'll do that, when
+      merging into master)
+    - it's always a good idea to have a look at 'git log' to get an idea how to
+      format its own commits
+
+Examples
+--------
+
+Bad:  "fixed loop to start from 0 instead of 1"
+Good: "Avoid off-by-one issue in skiplist loop"
+
+Bad:  "fixed typo"
+Good: "Docs: typo"