controlspeed 2.3

Control function call speed ,support network mode by redis

# ControlSpeed
这项目是用来控制函数调用的频率, 不仅支持本地的同步线程模式, 而且支持分布式模式.
[更多开发描述,请点击链接](http://xiaorui.cc)

ControlSpeed(本地版)还不兼容多进程多线程的场景, 当然你可以用ControlSpeedNetwork分布式版解决. 缺点是每次访问都会有一次网络io消耗.
#Usage:

装饰器使用方法
```
from controlspeed import ControlSpeed
@ControlSpeed(max_calls=10, period=1.0)
def do_something():
pass
```

with关键词控制上下文
```
from controlspeed import ControlSpeed
rate = ControlSpeed(max_calls=10, period=1.0)
for i in range(100):
with rate:
do_something()
```

支持回调函数的控速
```
from controlspeed import ControlSpeed
import time
def limited(until):
duration = int(round(until - time.time()))
print 'Speed limited, sleeping for %d seconds' % duration

rate = ControlSpeed(max_calls=2, period=3, callback=limited)
for i in range(3):
with rate:
print i
```

在2.1加入了分布式限频, 借助于redis实现.
```
import redis
redis_conn = redis.StrictRedis()
key = 'xiaorui.cc'

@ControlSpeedNetwork(redis_conn, key, max_calls=10, period=3.0)
def do_something(args):
print args
time.sleep(0.1)

for i in xrange(20):
do_something(i)
```