Update distro specific package installation instructions

- Back in Fedora 22 the distribution switched from using yum to dnf for
  package installation, while CentOS / RHEL continues to use yum.
  Separate out package instructions.

- Update package dependencies for what is required on current versions
  of the documented distributions.
4 jobs for version-info in 91 minutes and 32 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #262818
centos_build

00:15:15

passed #262819
ubuntu_build

00:44:02

 
  Test
passed #262820
centos_test

00:35:23

passed #262821
ubuntu_test

00:47:21