Need a Get-ElapsedTime kind of function

Something like 

``` powershell
function Get-ElapsedTime() {
  param(
     [Parameter(Mandatory = $true)]
     [ValidateNotNullOrEmpty()]
     [scriptblock] $chunk
  )

  $watch = [system.diagnostics.stopwatch]::StartNew()
  Invoke-Expression $chunk
  $watch.Stop()

  # print?
}
```
