Docs: Removing more GraphiQL information

Author: renatomefi

Resources/doc/definitions/graphiql/custom-http-headers.md

@@ -1,4 +1,6 @@
 GraphiQL
 ========
 
-* [Custom HTTP headers](custom-http-headers.md)
+GraphiQL is provided by the bundle [OverblogGraphiQLBundle](https://github.com/overblog/GraphiQLBundle)
+
+Follow its instructions in order to customize the headers

Resources/doc/definitions/graphiql/index.md

@@ -19,7 +19,7 @@ Default files location
 Yaml configuration
 -------
 
-For more examples on what can be done with Symfony Expression Language (the stuff after `@=`), check 
+For more examples on what can be done with Symfony Expression Language (the stuff after `@=`), check
 [here](expression-language.md) and [here](http://symfony.com/doc/current/components/expression_language/syntax.html).
 
 ```yaml
@@ -96,13 +96,14 @@ type | Path
 -----| -----
 simple request | `/graphql/foo`
 batch request | `/graphql/foo/batch`
-GraphiQL | `/graphiql/foo`
+GraphiQL* | `/graphiql/foo`
 
 **bar** schema endpoint can be access:
 
 type | Path
 -----| -----
 simple request | `/graphql/bar`
 batch request | `/graphql/bar/batch`
-GraphiQL | `/graphiql/bar`
+GraphiQL* | `/graphiql/bar`
 
+\* `/graphiql` depends on [OverblogGraphiQLBundle](https://github.com/overblog/GraphiQLBundle)