Bumped version number to 0.3-dev

Should have done this way earlier on the develop branch.
diff --git a/git-flow-version b/git-flow-version
index 349517e..93a0df2 100644
--- a/git-flow-version
+++ b/git-flow-version
@@ -36,7 +36,7 @@
 # policies, either expressed or implied, of Vincent Driessen.
 #
 
-GITFLOW_VERSION=0.2.1
+GITFLOW_VERSION=0.3-dev
 
 usage() {
 	echo "usage: git flow version"