Create some way to do stub a function a certain number of times

When making a stub, it may be desirable to only stub the function for a single call.

You can do this now, like:
```lua
local hookStub

hookStub = stub( hook, "Call" ).with( function()
hookStub:Restore()
end )

hook.Call( "blah" )

expect( hookStub ).to.haveBeenCalled()
```

But if you don't localize `hookStub` first, as would be common for these sorts of tests:
```lua
local hookStub = stub( hook, "Call" ).with( function()
hookStub:Restore()
end )
```
You would get an error on your `hook.Call` invocation, with the error message `attempt to index global 'hookStub', a nil value`.

This of course makes sense, but it can be confusing. Instead, perhaps we could have something like:
```lua
local hookStub = stubOnce( hook, "Call" )

hook.Call( "blah" )

expect( hookStub ).to.haveBeenCalled()
```

More realistically, we should allow a hook to be stubbed for any number of calls. Maybe as an optional third parameter to `stub()`?