Implemented case-insensitive search
differentiate between attributes w/ different types of matching

some attributes (description, period) can allow partial matches
("cretaceous" can match both "late cretaceous" and "early cretaceous"),
while others shouldn't (Dinodex#find(:walking, "ped") should not return any
matches)
prefer parens around method arguments
replace unused block arg with underscore
don't need @ to reference weight attr
reword specs, add csvs to spec/fixtures
add messages to pending specs