Display SSL errors

`curl -s` not only hides the progress bar, it also hides errors. `-S` makes the errors show up again.

README.md

@@ -13,7 +13,7 @@ Installation / Usage
 1. Download the [`composer.phar`](https://getcomposer.org/composer.phar) executable or use the installer.
 
     ``` sh
-    $ curl -s https://getcomposer.org/installer | php
+    $ curl -sS https://getcomposer.org/installer | php
     ```
 
 
@@ -123,4 +123,4 @@ Acknowledgments
 - This project's Solver started out as a PHP port of openSUSE's
   [Libzypp satsolver](http://en.opensuse.org/openSUSE:Libzypp_satsolver).
 - This project uses hiddeninput.exe to prompt for passwords on windows, sources
-  and details can be found on the [github page of the project](https://github.com/Seldaek/hidden-input).
+  and details can be found on the [github page of the project](https://github.com/Seldaek/hidden-input).