Allow me to use the logic that creates nodes without having to attach th...

...em

This is a pretty simple PR that allows me to create nodes in-memory but not in the DOM. I find jasmine-fixture to be really useful, but I also have plenty of tests to do where I'm passing around nodes that may not be attached (they came from the server, or were constructed by a template, etc).

Enables something like this:
```
describe 'FooBar', ->
  it 'adds new elements to the existing content', ->
    affix('#root') #as before
    newContent = create('#root #child', false) #now I can do this!
    fb = new FooBar(newContent)
    ...
```