I think Teemo can be played and played well with an AD setup, but I also feel like there are champions who do it better than him. Teemo has nothing that benefits an AD build, except for a very situational attack speed buff from his passive. Therefore I agree with ThePonsterMenis.
I generally build Teemo as either a hybrid damage dealer (Gunblade, Guinsoo's) to take advantage of high AS, or an on-hit shredder (Malady, BC, Hurricane, BotRK).
You can also build Teemo as almost a tanky AD fighter (Frozen Mallet and such) to be able to get that blind onto the enemy carry, disabling them.
Of course, there's the AP build, which just makes your shrooms the worst thing to step on since burning poop.
Summary: Teemo doesn't have anything that scales off AD or reliably increases attack speed, so he can't ADC. Regardless, Teemo is a very flexible and versatile champion that can, in all honesty, do everything at the same time. I can basically take a list of items that will work on Teemo, point at 6 items, and have it be decent in a lot of situations.