Version 0.2.0

Redefined the way all the methods and indicators are creating. Now instead of simple "give me that thing or panic" you receive complete rust-way Result.

• added MedianAbsDev method;
• added MeanAbsDev method;
• optimized StDev method;
• fixed missed docs warning when period_type_# feature enabled;
• SignalType forced to be always u8;
• added optional unsafe perfomance blocks;
• changed OHLC's TR-method template;
• optimized Conv method;
• modifed OHLC(V) validation;
• optimized SMM method;
• added over method on IndicatorInitializer;
• optimized SWMA method;
• small WMA method optimization;
• fixed highest/lowest methods when value is NaN;
• fixed SMM method when value is NaN;
• added Detrendede Price Oscillator indicator.