Abstract Class

[jwilber]

Originally I wanted to create a chart Abstract Base Class with the common methods across the charts (e.g. resolveFont(), initChartValues(), setSVG(), resolveData(), etc.) but didn't find a straightforward manner of doing so in ES6. I'm sure it can be done easily enough with prototypal inheritance, but I'd prefer to keep everything as ES6 as possible.

I don't write too much JavaScript, so it's pretty likely that I missed something. Very open to any ideas!

[laimonasA]

I can have a go at refactoring it to just a basic Chart class which contains these common methods and possibly some of the shared properties, these other classes will then inherit the methods and properties.