Use document fragment on iterator binding

This is an attempt to speed up the `IteratorBinding` by first appending all nodes to a document fragment and then appending that in one operation to the DOM.  Watson `IteratorBinding` test results are as follows:

```
IteratorBinding performance: loop over an array of 150 items:

Result on v0.14.1-112-gddc8858: 44.0854 +- 3.12568 [iterator-binding-speed] Use document fragment on iterator binding (Kristian PD)
Result on v0.14.1-111-g755c1f1: 29.8287 +- 3.34842 [remotes/origin/master] Bump watson 
(Harry Brundage)

IteratorBinding performance: loop over an array of 100 items:

Result on v0.14.1-112-gddc8858: 26.070800000000002 +- 2.49562 [iterator-binding-speed] Use document fragment on iterator binding (Kristian PD)
Result on v0.14.1-111-g755c1f1: 18.570300000000003 +- 2.67934 [remotes/origin/master] Bump watson (Harry Brundage)

IteratorBinding performance: loop over an array of 50 items:

Result on v0.14.1-112-gddc8858: 12.5822 +- 3.44362 [iterator-binding-speed] Use document fragment on iterator binding (Kristian PD)
Result on v0.14.1-111-g755c1f1: 9.9369 +- 3.34279 [remotes/origin/master] Bump watson (Harry Brundage)
```

waiting on test suite improvements by @hornairs to fully assert this is an improvement