Log Message:
Update py-pandas-datareader to 0.5.0

Changes:

- Compat with the new Yahoo iCharts API. Yahoo removed the older API,
  this release restores ability to download from Yahoo.
- ``DataReader`` now supports Quandl.
- Removed Oanda as it became subscription only.
- web sessions are closed properly at the end of use
- Handle commas in large price quotes
- Test suite fixes for test_get_options_data
- Test suite fixes for test_wdi_download
- avoid monkey patching requests.Session
- `get_data_yahoo` now treats ``'null'`` strings as missing values