Install Prestissimo in Workspace

**Why we need this change?**

[Prestissimo](https://github.com/hirak/prestissimo) will enabled `composer` to install plugins in parallel.

**Source**

http://jackmcdade.com/blog/tired-of-waiting

env-example

@@ -77,6 +77,7 @@ WORKSPACE_INSTALL_WORKSPACE_SSH=false
 WORKSPACE_INSTALL_LARAVEL_ENVOY=false
 WORKSPACE_INSTALL_LARAVEL_INSTALLER=false
 WORKSPACE_INSTALL_DEPLOYER=false
+WORKSPACE_INSTALL_PRESTISSIMO=false
 WORKSPACE_INSTALL_LINUXBREW=false
 WORKSPACE_INSTALL_MC=false
 WORKSPACE_INSTALL_SYMFONY=false