minor readme update
adds zlib-1.2.7 and enables few modules

NGX_FILE_AIO
NGX_IPV6
HTTP_DAV
HTTP_SECURE_LINK
HTTP_FLV
HTTP_MP4
HTTP_GUNZIP
HTTP_GZIP_STATIC
MAIL
MAIL_SSL
HTTP_REALIP
HTTP_STUB_STATUS
ZLIB
PCRE_JIT