add git commit template (#18)

motivation: missing the template mentioned in the contribution guides

changes: add dev directory with the git commit template

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.