DOC-248 Revised and updated readme for stdlib module
DOC-248 Revised and updated readme for stdlib module

Reorganized and edited stdlib module readme.

DavidS/puppetlabs-stdlib,fuel-infra/puppetlabs-stdlib,yadavnikhil/puppetlabs-stdlib,puppetlabs/puppetlabs-stdlib,HelenCampbell/puppetlabs-stdlib,jbondpdx/puppetlabs-stdlib