Update "setting" section of README
Update "setting" section of README

Update the "setting" section of the README to explain the
syntax for nested setting hierarchies.

mhaskel/puppetlabs-hocon,underscorgan/puppetlabs-hocon,fpringvaldsen/puppetlabs-hocon,HAIL9000/puppetlabs-hocon,puppetlabs/puppetlabs-hocon