add finagle like service/filter

Call our finagle "Crack"
add Crack to _oasis
express Handler, Middleware in terms of Crack
update comments
add apply_all{,'} to crack
change rock to use crack
move crack to rock

one cutesy name is enough
remove reference to missing module
add homepage to _oasis
split opium into 2 libs

opium and opium_rock
META is generated by _oasis
new target to clean all
update oasis to reflect 2 libs
remove pipe_extra