Added a nicer way of installing/uninstalling git-flow.

Now also installs the shFlags.sh script. (The license lines are included in its header.)
diff --git a/git-flow b/git-flow
index ef73c69..4ff458b 100755
--- a/git-flow
+++ b/git-flow
@@ -54,7 +54,7 @@
 	fi
 
 	# use the shFlags project to parse the command line arguments
-	. "$GITFLOW_DIR/shFlags/src/shflags"
+	. "$GITFLOW_DIR/shFlags.sh"
 	#DEFINE_boolean quiet 0 'run without output' q
 	#DEFINE_boolean verbose 0 'run verbose (more output)' v
 	FLAGS "$@" || exit $?