Added 'feature checkout' subcommand.

This can be used as a shortcut to "git checkout feature/full-feature-name".
Feature branch prefix names may be used for convenience.

git-flow-feature

@@ -49,6 +49,7 @@ usage() {
 	echo "       git flow feature track <name>"
 	echo "       git flow feature diff [<name|nameprefix>]"
 	echo "       git flow feature rebase [-i] [<name|nameprefix>]"
+	echo "       git flow feature checkout [<name|nameprefix>]"
 }
 
 cmd_default() {
@@ -389,6 +390,17 @@ cmd_diff() {
 	fi
 }
 
+cmd_checkout() {
+	parse_args "$@"
+
+	if [ "$NAME" != "" ]; then
+		expand_nameprefix_arg
+		git checkout "$BRANCH"
+	else
+		die "Name a feature branch explicitly."
+	fi
+}
+
 cmd_rebase() {
 	DEFINE_boolean interactive false 'do an interactive rebase' i
 	parse_args "$@"