text: Title: ImportError: cannot import name 'SIGHUP' from 'signal'
  Body: Hi,
  
  After clone this git and done pip install cryptofeed[all] + python setup.py install
  
  I am trying to run Basic usage code 
  
  
  ```
  from cryptofeed import FeedHandler
  # not all imports shown for clarity
  
  fh = FeedHandler()
  
  # ticker, trade, and book are user defined functions that
  # will be called when ticker, trade and book updates are received
  ticker_cb = {TICKER: TickerCallback(ticker)}
  trade_cb = {TRADES: TradeCallback(trade)}
  gemini_cb = {TRADES: TradeCallback(trade), L2_BOOK: BookCallback(book)}
  
  
  fh.add_feed(Coinbase(pairs=['BTC-USD'], channels=[TICKER], callbacks=ticker_cb))
  fh.add_feed(Bitfinex(pairs=['BTC-USD'], channels=[TICKER], callbacks=ticker_cb))
  fh.add_feed(Poloniex(pairs=['BTC-USDT'], channels=[TRADES], callbacks=trade_cb))
  fh.add_feed(Gemini(pairs=['BTC-USD', 'ETH-USD'], channels=[TRADES, L2_BOOK], callbacks=gemini_cb))
  
  fh.run()
  ```
  
  But got an error "ImportError: cannot import name 'SIGHUP' from 'signal' 