strategy:turtle: add turtle framework

Turtle framework provides a set of basic methods, e.g, tr, atr and
attributes which might be used by child strategies. This framework
aims to save time and code to rewrite a modified turtle strategy
(child strategy), so any child strategy also should inherit this
class and redefine some keys methods to drive this framework to run.

Signed-off-by: Zhengwang Ruan <ruan.zhengwang@gmail.com>