Replace SSL with TLS

[nathansalter]

$ grep -rEi '\bSSL\b' EditorsDraft/
EditorsDraft/index-interim.html:All HTTP requests and responses SHOULD be secured using SSL.
EditorsDraft/edit.html:Although this specification does not mandate a specific means of securing an API, it does mandate that at a minimum all HTTP requests and responses MUST be secured using SSL.
EditorsDraft/edit-old.html:All HTTP requests and responses SHOULD be secured using SSL.
EditorsDraft/index-old.html:All HTTP requests and responses SHOULD be secured using SSL.