edit documentation: replace absolute links with relative links and fix a
couple of broken links

	modified:   CLA_Process.md
	modified:   CONTRIBUTING.md
	modified:   README.md
	modified:   doc/basic_config.md
	modified:   doc/build_install.md
	modified:   doc/centos_6_5_env.md
	modified:   doc/centos_7_env.md
	modified:   doc/design.md
	modified:   doc/detailed_config.md
	modified:   doc/dev_info.md
	modified:   doc/gtest.md
	modified:   doc/sending_messages.md
	modified:   doc/status_monitoring.md
	modified:   doc/troubleshooting.md
	modified:   doc/ubuntu_14_and_13_env.md