Quick install instructions on YDK-Py documentation differs from quick install instructions on YDK-Py README.

Code blocks for CentOS installation are not rendering correctly on YDK-Py documentation

Instructions for installation on other platforms are unnecessarily complex. Users shouldn't need to be directed to artifactory repos. They should be able to rely on pypi.org packages. Separate installation of core package should be described as optional if a model bundle is chosen since the core package is a dependency handled by Python packaging.