Changes with nginx 1.7.3 08 Jul 2014

    *) Feature: weak entity tags are now preserved on response
       modifications, and strong ones are changed to weak.

    *) Feature: cache revalidation now uses If-None-Match header if
       possible.

    *) Feature: the "ssl_password_file" directive.

    *) Bugfix: the If-None-Match request header line was ignored if there
       was no Last-Modified header in a response returned from cache.

    *) Bugfix: "peer closed connection in SSL handshake" messages were
       logged at "info" level instead of "error" while connecting to
       backends.

    *) Bugfix: in the ngx_http_dav_module module in nginx/Windows.

    *) Bugfix: SPDY connections might be closed prematurely if caching was
       used.