All versions of PHP msgpack are beta, be explicit about which version to install

Author: sodabrew

.travis/travis.sh

@@ -239,8 +239,11 @@ case $ACTION in
         install_igbinary
 
         # Install msgpack extension
-        # install_msgpack
-        pecl install msgpack
+        if [[ "$TRAVIS_PHP_VERSION" < "7.0" ]]; then
+            pecl install msgpack-0.5.7
+        else
+            pecl install msgpack-2.0.1
+        fi
 
         install_memcached
         run_memcached