add explanatory comments
force build from local gem; do not download
generate-key-pair script name has changed
add section comments
bundle install is not needed
model version has changed
update eventmachine dependency
make gem dependency of rpm/deb
set package name
default target is libertree-backend-x.x.x.{deb,rpm}
make built rpm/deb packages prerequisites for libertree-backend
remove unused FORCE target
replace "rpm" with PKG_TYPE
replace gem targets with PKG_TYPE targets