Fixed typo

doc/00-intro.md

@@ -49,7 +49,7 @@ any version beginning with `1.0`.
 #### Locally
 
 To actually get Composer, we need to do two things. The first one is installing
-Composer (again, this mean downloading it into your project):
+Composer (again, this means downloading it into your project):
 
     $ curl -s https://getcomposer.org/installer | php