test: removed test subsystem

Since the tests under this subsystem are out of date, remove test subsystem to
save efforts to maintain.

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

Regression subsystem only contains some modules used to import trading data to
database long time ago, and they are useless now, so remove it to save efforts
to maintain.

Signed-off-by: Zhengwang Ruan <ruan.zhengwang@gmail.com>
all: replace __exit__ with __del__

This is a bug that __exit__() not be called when instances are destroied, fix it
by replacing it with __del__.

Signed-off-by: Zhengwang Ruan <ruan.zhengwang@gmail.com>
strategy:futures: add __openPosition and __closePosition

There are too much redundant codes in this module which brought difficulties to
maintain and develop new features, so put those codes in some common calls to
keep the whole framework as clear as possible.

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