Vol 2. ch1. IoC Container & DI. p54.
Vol 2. ch1. IoC Container & DI. p55.
Revert "Vol 2. ch1. p54."

This reverts commit 699fc80303169fe4970915bd4cda65ae0d9db9bd.
Revert "Revert "Vol 2. ch1. p54.""

This reverts commit 8c18e5851ef81dc16e1157302e20f02c5cae7d40.
Merge branch 'master' into orginal_head