get_nasdaq_symbols never returns

Hi there!

The only symbols I'm able to retrieve are S&P 500.

Everything else never returns (no error, just takes forever).
Example:
```
sp500 = finsymbols.get_sp500_symbols() ## This works
nasdaq = finsymbols.get_nasdaq_symbols() ## never returns
amex = finsymbols.get_amex_symbols() ## never returns
```

