Improved loaders documentation

doc/Loaders.md

@@ -1,8 +1,34 @@
 Loaders
 =======
-The loaders are responsible to save or output your transformed data.
+The loaders are responsible to save or output your transformed data. Here are some built-in loaders, feel free to implement your own ones.
 
-Feel free to implement your own ones.
+
+ArrayLoader
+-----------
+This loader stores your data into an array.
+
+DebugLoader
+-----------
+At the end of the process, this loader `var_dump` your data. You can use another debug function in the constructor if needed.
+
+FileLoader
+----------
+This loader saves your data in a file. Make sure your transformer adds a `PHP_EOL` if you want a line for each load (you can also hook on the `ETLEvents::AFTER_TRANSFORM` event)
+
+CsvFileLoader
+-------------
+This loader will take your `SplFileObject` and call `fputcsv` on each load.
+
+JsonFileLoader
+--------------
+This loader will store your data as a Json file.
+
+
+Loaders and FlushableLoaders
+============================
+By default, each loader will store your data when invoked.
+
+You can create your own loader by implementing `BenTools\ETL\Loader\FlushableLoaderInterface`, which will cause the loader to buffer elements and store them only when the `flush()` method is called (cf. `BenTools\ETL\Loader\DoctrineORMLoader`).
 
 
 Next: [Events](Events.md)