Fix location of README file for rpm/deb

The file suffix was changed but package building instructions were
missed.

distribution/packages/build.gradle

@@ -131,7 +131,7 @@ Closure commonPackageConfig(String type, boolean oss, boolean jdk) {
         with binFiles(type, oss, jdk)
       }
       from(rootProject.projectDir) {
-        include 'README.textile'
+        include 'README.asciidoc'
         fileMode 0644
       }
       into('lib') {