trade_rsi: RSI Trading Signal
In msaltieri/algotrading: Algorithmic Trading with R

This is a strategy for long/short positioning according to RSI cross of pre-fixed thresholds subject to parameterization.

1	trade_rsi(series, lower = 30, upper = 70, epsilon = 5/100)

`series`	is a `xts` object representing the OHLC object as retrieved using `getSymbols`.
`lower`	is the RSI level requested to trigger the short trade.
`upper`	is the RSI level requested to trigger the long trade.
`epsilon`	is the tolerance to avoid closing a position too early.