v0.4.21

• Add ability to specify multiple measurements from the same page load by
  setting the measurement property in the JSON config file to an array. For
  example, you can now use the performance API to define two intervals on the
  same page, and compare them to each other or to other pages.

• Add ability to pull measurements from the browser performance measurement API,
  e.g.:

  "benchmarks": [
    {
      "measurement": {
        "mode": "performance",
        "entryName": "foo"
      }
    }
  ]
  

• Add new syntax for specifying benchmarks:

  "benchmarks": [
    {
      "measurement": {
        "mode": "callback"
      }
    },
    {
      "measurement": {
        "mode": "expression",
        "expression": "window.tachometerResult"
      }
    }
  ]
  

• Fix main entry in package.json to point to lib/cli.js.

• Added more fields to JSON output file to more closely match table printed to the console

• Fix default benchmark name on Windows to replace all \\ with /. For
  example, previously a benchmark name might have been
  "src/test\\data\\for-loop.html". With this fix, the benchmark name will now be
  "src/test/data/for-loop.html".