TimeDelta and quantity input checking

A TypeError is raised when passing in a TimeDelta to a function decorated with the quantity input decorator and a time-like type annotation for the input.

The code below illustrates the issue. To me it seems natural to pass in a TimeDelta object as a way of expressing a duration, but perhaps I using TimeDelta incorrectly.

```
import astropy.units as u
from astropy.time import Time

@u.quantity_input
def f(t: u.s):
print(t)

dt = Time('2018-10-09') - Time('2018-10-08')

f(dt)
```

Start by reproducing the example involving the quantity_input decorator, the u.s time-like annotation, and the TimeDelta value. Then inspect the decorator's input checking and time-like type handling; done means the intended TimeDelta behavior is established and the example no longer raises an unexpected TypeError.

Written by the indexing model from the issue text.