Add installation note

Author: patrickbrouwers

README.md

@@ -14,13 +14,16 @@
 
 *A fluent mapping driver for Doctrine2*
 
+```
+composer require laravel-doctrine/fluent
+```
+
 This mapping driver allows you to manage your mappings in an Object Oriented approach, separating your entities
 from your mapping configuration without the need for configuration files like XML or YAML.
 This is done by implementing the `LaravelDoctrine\Fluent\Mapping` interface, or extending the abstract classes
 provided with this package for an easier use:
 `LaravelDoctrine\Fluent\EntityMapping`, `LaravelDoctrine\Fluent\EmbeddableMapping` or `MappedSuperClassMapping`.
 
-
 This package provides a fluent Builder over Doctrine's `ClassMetadataBuilder`, aimed at easing usage of
 Doctrine's mapping concepts in Laravel. The builder adds syntax sugar and implements the same grammar that you
 might use in Laravel migrations.