add Composer 0.9.0 release (#352)

diff --git a/_layouts/downloads.html b/_layouts/downloads.html
index 13decc1..df157c0 100644
--- a/_layouts/downloads.html
+++ b/_layouts/downloads.html
@@ -329,6 +329,29 @@
                         </p>
                       </div>
 
+                      <div class="project-structure-repo theme-darksalmon">
+                        <h5>OpenWhisk Composer</h5>
+                        <p>Composer is a new programming model for composing cloud functions built on OpenWhisk</p>
+                        <p class="repo-title border-darksalmon">
+                          <a
+                            href="https://www.apache.org/dyn/closer.lua?filename=incubator/openwhisk/apache-openwhisk-0.9.0-incubating/openwhisk-composer-0.9.0-incubating-sources.tar.gz&action=download">
+                            Source code
+                          </a>
+                        </p>
+                        <p class="repo-title border-darksalmon">
+                          <a
+                            href="https://www.apache.org/dist/incubator/openwhisk/apache-openwhisk-0.9.0-incubating/openwhisk-composer-0.9.0-incubating-sources.tar.gz.sha512">
+                            SHA-512 checksum
+                          </a>
+                        </p>
+                        <p class="repo-title border-darksalmon">
+                          <a
+                            href="https://www.apache.org/dist/incubator/openwhisk/apache-openwhisk-0.9.0-incubating/openwhisk-composer-0.9.0-incubating-sources.tar.gz.asc">
+                            PGP signature
+                          </a>
+                        </p>
+                      </div>
+
                       <div class="project-structure-repo theme-darkorange">
                         <h5>OpenWhisk Apigateway</h5>
                         <p>A performant API Gateway based on Openresty and NGINX.</p>