Ensure proper poly-filling is being done when needed.

[Lazerbeak12345]

• Use babel to apply polyfills.
• (once again) Attempt migration to parcel #65
• Failing the above, use the babel-typescript parser to speed up the build process.

[Lazerbeak12345]

See b4b4e2b for recent push to include Babel.

Mixed results from babel. The biggest issue is that I'd like to have a version of the libarary that includes all needed polyfills for the default browserslist, but it's not easy to make that work.

I've also attempted (but not pushed) a change that would move this to tye rollup-babel plugin instead of gulp-babel. There's actually a few good reasons to do that, but as I'd like to try parcel again, I'll hold off for a bit.

[Lazerbeak12345]

Closed by #67