SortedArraySet#length not updating

[cbarrick]

SortedArraySet#length doesn't update when you .pop() and .shift()

Here's an example from the Node REPL:

> var SortedArraySet = require('collections/sorted-array-set')
undefined
> var a = new SortedArraySet()
undefined
> a.add('foo')
true
> a.add('bar')
true
> a.length
2
> a.pop()
'foo'
> a.shift()
'bar'
> a.length
2
> a.length === a.array.length
false
> a
{ array: [],
  contentEquals: [Function],
  contentCompare: [Function],
  getDefault: [Function],
  length: 2 }
>