Add method.py

Added method.py

method.py released.
method.py inherits from ftx.py and adds some preprocessing.
You can easily and shortly make bots.

I fixed some bugs.

Arrange code

2.2

Update README.md

Add functions

Hava a nice day!

2021/04/30 Bug fixed.

First release

Pybottersが便利なので、とりあえずFTX用のラッパーを作りました。まだまだ機能が不十分なので作っていきます。