update ChangeLog for 2.2.0 release

ChangeLog

@@ -1,3 +1,28 @@
+2018-10-9 v2.2.0
+
+* NEW support TLS 1.3.
+* NEW support 0-RTT in TLS 1.3.
+* NEW TLS 1.3 requires OpenSSL version >= 1.1.1
+* NEW TLS 1.3 support autodetected and enabled at compile time. No special configuration needed.
+* NEW counters v13, v12, v10 - breakdown of slh & slc requests into TLS versions.
+  # of requests in TLS 1.3, TLS 1.2 and TLS 1.0 respectively.
+* NEW indicator of TLS 1.3 support on servstats page.
+  `no_tls1_3` when compiled against OpenSSL <= v1.1.0.
+  `tls1_3` when compiled against OpenSSL >= 1.1.1
+* NEW counter ucb - bad certificates as reported by clients.
+* NEW counter ush - shutdown by clients after ServerHello.
+* NEW log "shutdown after ServerHello" on LEVEL 2.
+* NEW log "Handshake failed: socket i/o error" on LEVEL 2.
+* NEW log "Handshake failed: reached max retries" on LEVEL 2.
+* CHANGED enhance uniqueness of serial numbers for generated certificates.
+* CHANGED much faster logging to syslog.
+* CHANGED relax memory pool restriction for better multithread performance 
+* CHANGED increase number of retries in TLS handshakes.
+* CHANGED improve accuracy in processing time of requests recovered from initially failed handshakes.
+* FIXED various complaints from musl libc on Alpine Linux (contributed by JohnNilsson on Github; issue #16)
+* FIXED clean up compile warnings seen on newer platforms
+* FIXED replace deprecated OpenSSL APIs
+
 2018-6-20 v2.1.2
 
 * NEW support "--enable-static" for building static binary using GNU Autotools. (Issue #13)