Allow accel functions to be queued before "ready" event is fired.

This PR extends the use of `sync-queue` to enable no destructive functions to fire until `ready` is emitted. As a fallout of that, this now works:

```js
/* test rig */ var t = 1, tmax = 5
function ok (a, d) { console.log(a ? 'ok ' + (t++) + ' -' : 'not ok ' + (t++) + ' -', d); }
console.log(t + '..' + tmax);

/* script */

var tessel = require('tessel');
var accel = require('accel-mma84').use(tessel.port['A']);

// No need to wrap this in on('ready') anymore!
accel.on('sample', function (xyz) {
  console.log(xyz);
});

```