TTR version 0.21-1
  Changes from version 0.21-0

NEW FEATURES:

- None.


CHANGES:

- Attempted to make stockSymbols more robust to nasdaq.com changes.


BUG FIXES:

- Fixed stockSymbols for nasdaq.com changes (again).

- Corrected final calculation in Yang-Zhang volatility, thanks to Shal Patel.

- Corrected k in Yang-Zhang volatility, thanks to Ian Rayner.

- Corrected s2o and s2c in Yang-Zhang volatility, thanks to Ian Rayner.

- Corrected KST when input is xts (res is now * 100), thanks to Yuanwei

