Broken links to offline ClusterHQ infrastructure

[wallrj]

https://travis-ci.org/ScatterHQ/flocker/jobs/189902204

build/docs-linkcheck/output.txt[24] gettinginvolved/contributing.rst:27: [broken] http://build.clusterhq.com/: HTTPConnectionPool(host='build.clusterhq.com', port=80): Max retries exceeded with url: / (Caused by NewConnectionError('<requests.packages.urllib3.connection.HTTPConnection object at 0x7fab7979d050>: Failed to establish a new connection: [Errno 110] Connection timed out',))
25: build/docs-linkcheck/output.txt[25] gettinginvolved/contributing.rst:100: [broken] http://build.clusterhq.com/: HTTPConnectionPool(host='build.clusterhq.com', port=80): Max retries exceeded with url: / (Caused by NewConnectionError('<requests.packages.urllib3.connection.HTTPConnection object at 0x7fab78b28690>: Failed to establish a new connection: [Errno 110] Connection timed out',))
27: build/docs-linkcheck/output.txt[27] gettinginvolved/infrastructure/release-process.rst:9: [broken] http://clusterhq-staging-docs.s3.amazonaws.com/master/gettinginvolved/infrastructure/release-process.html: 403 Client Error: Forbidden for url: http://clusterhq-staging-docs.s3.amazonaws.com/master/gettinginvolved/infrastructure/release-process.html
30: build/docs-linkcheck/output.txt[30] gettinginvolved/infrastructure/release-process.rst:224: [broken] http://build.clusterhq.com/boxes-flocker: HTTPConnectionPool(host='build.clusterhq.com', port=80): Max retries exceeded with url: /boxes-flocker (Caused by NewConnectionError('<requests.packages.urllib3.connection.HTTPConnection object at 0x7fab79010ed0>: Failed to establish a new connection: [Errno 110] Connection timed out',))