Inaccurate MACD indicator calculator

[yaro90]

I'm submitting a...

• bug

What is the current behaviour

Signal line is calculated before the macd itself which skews future values once macd becomes available.

What is the expected behaviour

Signal is an EMA of macd, calculation can only start once we have a sufficient number of macds.

Please tell us about your environment

• Version: 2.0.1
• Browser: [all | Chrome XX | Firefox XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari ]

Other information

[yaro90]

@markmcdowell Would be great to have a release with the fix from PR #694 included. Thank you.