Provide a git commit template. (#508)

* Provide a git commit template.

Motivation:

It should be possible to understand what has changed and the reason
those changes were made from reading a commit message.

Modifications:

Add the git commit template used by NIO.

Result:

Commit messages should be more useful as they must follow the given
template.

* Make each section a markdown subtitle

dev/git.commit.template

@@ -0,0 +1,14 @@
+One line description of your change
+
+### Motivation:
+
+Explain here the context, and why you're making that change.
+What is the problem you're trying to solve.
+
+### Modifications:
+
+Describe the modifications you've done.
+
+### Result:
+
+After your change, what will change.