Update build steps in README to work with latest 0.8
Update build steps in README to work with latest 0.8

Shopify/poseidon,airbnb/poseidon,apptentive-engineering/poseidon,codeclimate/poseidon,Tapjoy/poseidon,bpot/poseidon,ListenFirstMedia/poseidon,SponsorPay/poseidon,chingor13/poseidon,gjackson12/poseidon,nepalez/poseidon