Housekeeping on respond.js - no version change

Sources: https://github.com/scottjehl/Respond/releases/*.zip

Added 5x missing respond-proxy.html - builds on
https://github.com/cdnjs/cdnjs/pull/2178, addresses
https://github.com/cdnjs/cdnjs/issues/1948 and also
https://github.com/cdnjs/cdnjs/issues/1939

Added missing respond.js (not min’d) to 1.1.0