Add sections to README for why, authorization, writing adapters and handlers, and testing.
Add sections to README for why, authorization, writing adapters and handlers, and testing.

litaio/lita,chriswoodrich/lita,tristaneuan/lita,sadiqmmm/lita,byroot/lita,litaio/lita,brodock/lita,liamdawson/lita,PatrickTulskie/lita,sadiqmmm/lita,natesholland/lita,brodock/lita,elia/lita,jimmycuadra/lita,MatthewKrey/lita,tristaneuan/lita,natesholland/lita,jaisonerick/lita,jimmycuadra/lita,chriswoodrich/lita,prsimp/lita,crimsonknave/lita,jaisonerick/lita,MatthewKrey/lita,liamdawson/lita,byroot/lita,crimsonknave/lita,elia/lita,mcgain/lita,mcgain/lita