New Twiddle

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  dataPoints: [
    { id: 0, start: 1, end: 10 },
    { id: 1, start: 8, end: 20 },
    { id: 2, start: 25, end: 30 }
  ],
  lowerLimit: Ember.computed('dataPoints.[]', function() {
    return Math.min(...this.get('dataPoints').mapBy('start'));
  }),
  upperLimit: Ember.computed('dataPoints.[]', function() {
    return Math.max(...this.get('dataPoints').mapBy('end'));
  }),
  colors: [
    'red',
    'green',
    'blue'
  ]
});

application.template.hbs

<style type="text/css">
rect:hover {
  stroke-width: 4px;
}
</style>
<svg style="width: 100%; padding: 5px;" >
{{#each dataPoints as |point|}}
  <rect x="{{scale point.start lowerLimit upperLimit}}%" height="20px" width="{{scale (subtract point.end point.start) lowerLimit upperLimit}}%" stroke="black" fill={{pick-from colors point.id}} fill-opacity=0.5 />
{{/each}}
</svg>

helpers.pick-from.js

import Ember from 'ember';

export function pickFrom([list, index]/*, hash*/) {
  return list[index % list.length];
}

export default Ember.Helper.helper(pickFrom);

helpers.scale.js

import Ember from 'ember';

export function scale([value, lowLimit, highLimit]/*, hash*/) {
  return 100 * (value - lowLimit) / (highLimit - lowLimit);
}

export default Ember.Helper.helper(scale);

helpers.subtract.js

import Ember from 'ember';

export function subtract([a,b]/*, hash*/) {
  return a-b;
}

export default Ember.Helper.helper(subtract);

twiddle.json

{
  "version": "0.5.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.2.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}