configure Ember app build targets

[0xadada]

Configure Ember build targets such that the build is slim and optimized for the proper set of browsers to support.

In {{configure/targets.js}}, Ember will use Babel to transpile code for browsers listed in the targets array.

h2. Supported list

browserl.ist/?q=>+1.5%25+in+US
> 1.5% in US

Tasks

• Determine optimal set of browsers to support
• Update testem.js to test supported browsers
• Update Browser-Support statement

Testem.js

const chromeArgs = [
  '--disable-gpu',
  '--headless',
  '--remote-debugging-port=9222',
  '--window-size=1024,768'
];

module.exports = {
  test_page: 'tests/index.html?hidepassed',
  disable_watching: true,
  launch_in_ci: [
    'Chrome'
  ],
  launch_in_dev: [
    'Chrome',
    'Chrome Canary',
    'Firefox',
    'Safari'
  ],
  'browser_args': {
    'Chrome': chromeArgs,
    'Chrome Canary': chromeArgs,
    'Firefox': [
      '-headless', /* headless available on v55+ on Linux, 56+ on Windows/Mac */
      '--window-size=1024,768'
    ]
  }
};