Updated TextGeometry to use ES6 class format.

[jmschrack]

What kind of change does this PR introduce? (check at least one)

• Bugfix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Code style update
• Refactor (refactoring or adding test which isn't a fix or add a feature)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

Did you test your solution?

• I lightly tested it in one browser
• I deeply tested it in several browsers
• I wrote tests around it (unit tests, integration tests, E2E tests)

I tested all the provided samples in Edge, Chrome, and Firefox. They all worked fine. 👍

Problem Description

Three-bmfont-text is incompatible with ES6 classes.
See: #46

Solution Description

var Base = THREE.BufferGeometry
function TextGeometry (opt) {
  Base.call(this)
...
}
inherits(TextGeometry, Base);

was changed to

class TextGeometry extends THREE.BufferGeometry {
  constructor(opt){
    super(opt);
...
  }
}

Side Effects, Risks, Impact

• N/A

Aditional comments:

[jtbandes]

@mattdesl would you be able to review this PR? Looks like #46 prevents use with versions of three.js that internally use ES6 classes.

[kkota1]

Did the owner die or something. Good PR

[jtbandes]

I ended up making a separate package for text rendering. Check it out at: https://github.com/foxglove/three-text Will publish to NPM shortly.