Forecast Oscillator (FOSC)

``` use foscrs::FOSC; use tacommon::traits::Indicator;

let mut fosc = FOSC::new(5); asserteq!(fosc.next(81.59), None); asserteq!(fosc.next(81.06), None); asserteq!(fosc.next(82.87), None); asserteq!(fosc.next(83.00), None); asserteq!(fosc.next(83.61), None); asserteq!(fosc.next(83.15), Some(-1.2868310282621687)); asserteq!(fosc.next(82.84), Some(-1.6586190246257615)); asserteq!(fosc.next(83.99), Some(1.0346469817835624)); asserteq!(fosc.next(84.55), Some(1.0277942046126718)); asserteq!(fosc.next(84.36), Some(-0.0995732574679644)); asserteq!(fosc.next(85.53), Some(0.5997895475271895)); asserteq!(fosc.next(86.54), Some(0.6482551421308311)); asserteq!(fosc.next(86.89), Some(0.08286339049376355)); asserteq!(fosc.next(87.77), Some(0.157229121567756)); assert_eq!(fosc.next(87.29), Some(-1.5832283193950765));

```