Update CF environment variables link for ruby

[#73153838]
Update CF environment variables link for node.js

[#73153838]
Added links to Python, PHP, and Go source

* http://docs.cloudfoundry.org/buildpacks/

[#73153838]
Add links to github issues

[#73153838]
erge branch 'landing-page-links' of github.com:cf-buildpacks/docs-buildpacks into cf-buildpacks-landing-page-links

Conflicts:
	index.html.md.erb
	node/node-environment.html.md
	ruby/ruby-environment.html.md
Merge branch 'cf-buildpacks-landing-page-links'