[pandas] SSL certificate errors for World Bank Data

[mmcky]

This line seems to be failing on the latest coverage tests from last night.

govt_debt = wb.download(indicator='GC.DOD.TOTL.GD.ZS', country=['US', 'AU'], start=2005, end=2016).stack().unstack(0)

[mmcky]

@najuzilu would you have any time to look into this issue with the pandas lecture?

[najuzilu]

@mmcky this has been fixed.