use --no-dev flag when installing

Composer installs the dev requirements *as listed before running any scripts*
when executing `create-project`. By specifying `--no-dev`, we prevent that from
occurring.

This also adds a note that if you want development requirements, you *must* run
`composer update` on completion.

Author: weierophinney

doc/book/quick-start-skeleton.md

@@ -11,7 +11,7 @@ renderer, and error handler from the outset.
 First, we'll create a new project, using Composer's `create-project` command:
 
 ```bash
-$ composer create-project -s rc zendframework/zend-expressive-skeleton expressive
+$ composer create-project --no-dev -s rc zendframework/zend-expressive-skeleton expressive
 ```
 
 > ### Stability
@@ -20,6 +20,12 @@ $ composer create-project -s rc zendframework/zend-expressive-skeleton expressiv
 > to recognize the version as installable, you must pass the `-s rc` flag,
 > indicating it should use packages of RC stability.
 
+> ### Development requirements
+>
+> If you wish to use the development requirements as defined in the skeleton
+> (specifically, PHPUnit and PHP_CodeSniffer), you will need to run a
+> `composer update` after installation.
+
 This will prompt you to choose:
 
 - A router. We recommend using the default, FastRoute.