add .index() for list compat, updated exception messages, and added a silly test to show off slicing and indexing
add .index() for list compat, updated exception messages, and added a silly test to show off slicing and indexing

zeroSteiner/boltons,neuropil/boltons,siemens/boltons,mgaitan/boltons,suranap/boltons,markrwilliams/boltons,kevinastone/boltons,doublereedkurt/boltons