Issue with build_portfolio #136

Running basic example:

from finquant.portfolio import build_portfolio
names = ['GOOG', 'AMZN', 'MCD', 'DIS']
pf = build_portfolio(names=names, data_api="yfinance")
pf.properties()

Produces NaNs for all stocks except for the first in the list:

Stocks: AMZN, DIS, GOOG, MCD
Time window/frequency: 252
Risk free rate: 0.005
Portfolio Expected Return: 0.075
Portfolio Volatility: nan
Portfolio Downside Risk: nan
Portfolio Value at Risk: nan
Confidence level of Value at Risk: 95.00 %
Portfolio Sharpe Ratio: nan
Portfolio Sortino Ratio: nan

Skewness:
AMZN DIS GOOG MCD
0 0.987787 NaN NaN NaN

Kurtosis:
AMZN DIS GOOG MCD
0 -0.463871 NaN NaN NaN

Information:
Allocation Name
0 0.25 AMZN
1 0.25 DIS
2 0.25 GOOG
3 0.25 MCD

I tried

pf = build_portfolio(data=data), where I feed my own data, but the same behaviour is observed.

Similarlly
pf.returns.daily_returns() gives NaNs for all but the first column

finquant.returns.daily_returns(data) produces correct returns