EMA Cross Levels + Standard Deviation

Plots the price level that the most recent EMA crossover occurred at(Green if bullish and red if bearish).

Also calculates standard deviation over a shorter window-length/lookback period (of 'n_std_fast' length) and another over a much longer span of periods(n='n_std_slow', > 'n_std_fast').
These are the two dotted lines appearing as bands around the cross-level line.