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:

## big win ~ 30%
```
IteratorBinding performance: loop over an array of 150 items:

Result on v0.14.1-119-gdd9e834: 43.9752 +- 2.2106 [iterator-binding-speed] Defer some initialization until it's needed, remove unused method (Kristian PD)
Result on v0.14.1-111-g755c1f1: 30.7484 +- 3.4482 [remotes/origin/master] Bump watson (Harry Brundage)
```
## small win ~ 2%
```
parseNode function: 1000 divs without bindings

Result on v0.14.1-119-gdd9e834: 279.313 +- 1.04561 [iterator-binding-speed] Defer some initialization until it's needed, remove unused method (Kristian PD)
Result on v0.14.1-111-g755c1f1: 275.934 +- 0.731297 [remotes/origin/master] Bump watson (Harry Brundage)

Report: parseNode function: 1000 divs with 10 bindings

Result on v0.14.1-119-gdd9e834: 369.398 +- 3.82387 [iterator-binding-speed] Defer some initialization until it's needed, remove unused method (Kristian PD)
Result on v0.14.1-111-g755c1f1: 364.66700000000003 +- 3.76873 [remotes/origin/master] Bump watson (Harry Brundage)

```

waiting on test suite improvements by @hornairs to fully assert this is an improvement