Toggle code highlighting for broccoli-middleware >= 2.1.0

[astronomersiva]

This is needed to unlock ember-cli/broccoli-middleware#51

[astronomersiva]

Tried writing tests for this along the lines of

it('returns true when broccoli-middleware version is greater than or equal to 2.1.0', function() {
  this.addon.parent = {
    dependencies() { return { 'broccoli-middleware': '2.1.2' }; }
  };

  expect(this.addon._shouldHighlightCode()).to.be.true;
});

but _shouldHighlightCode() always returns false as the installed version of broccoli-middleware in node_modules is 1.2.1.

[astronomersiva]

@stefanpenner please take a look.

[astronomersiva]

@stefanpenner please take a look at this as well

[astronomersiva]

@stefanpenner a friendly ping :)

[astronomersiva]

@stefanpenner @rwjblue can you please take a look at this if you are free?

[stefanpenner]

@astronomersiva sorry for letting this sit, looks great!