Decaffeinate demo; fix sourcemaps

[davidgoli]

This removes the last of Coffeescript from the library entirely, converting the demo to Typescript.

It also converts the demo to rely on a Webpack build (the way a client app would in 2018) instead of direct-linking to the built rrule package via html.

This also addresses #303 .

[codecov-io]

Codecov Report

Merging #310 into master will decrease coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #310      +/-   ##
==========================================
- Coverage   89.91%   89.87%   -0.05%     
==========================================
  Files          28       28              
  Lines        1943     1945       +2     
  Branches      580      581       +1     
==========================================
+ Hits         1747     1748       +1     
- Misses        196      197       +1

Impacted Files	Coverage Δ
src/iter/index.ts	98.11% <100%> (-0.93%)	⬇️

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[davidgoli]

@AnthW I believe this addresses your sourcemap issue, would you please test this branch when you have a chance? Thanks!

[anthwinter]

@davidgoli I can confirm that this branch resolves the sourceMap issue. Thanks!