Catch BROKEN PIPE Error and retry current frame

Fix #24, #23 

Barely worker thread raises BROKEN PIPE error.  

Ex. in my environment
- 500,000 notifications sent
- 43 bad token detected and succeeded error handing
- 2 time failed to read error-response and raised BROKEN PIPE

So I added
- catch BROKEN PIPE errror
- Retry ```self.send``` when BROKEN PIPE error