minor #5911 Wrap all strings containing @ in quotes in Yaml (WouterJ)

This PR was merged into the 2.3 branch.

Discussion
----------

Wrap all strings containing @ in quotes in Yaml

| Q | A
| --- | ---
| Doc fix? | yes
| New docs? | no
| Applies to | all
| Fixed tickets | #5910

These where all strings I found with some simple grepping, I think we're pretty safe after merging this.

Commits
-------

40243a1 Wrap all strings containing @ in quotes in Yaml

Author: weaverryan

cookbook/bundles/best_practices.rst

@@ -342,7 +342,7 @@ The end user can provide values in any configuration file:
 
         # app/config/config.yml
         parameters:
-            acme_blog.author.email: fabien@example.com
+            acme_blog.author.email: "fabien@example.com"
 
     .. code-block:: xml
 

cookbook/email/dev_environment.rst

@@ -66,7 +66,7 @@ via the ``delivery_address`` option:
 
         # app/config/config_dev.yml
         swiftmailer:
-            delivery_address: dev@example.com
+            delivery_address: "dev@example.com"
 
     .. code-block:: xml
 

cookbook/logging/monolog_email.rst

@@ -31,10 +31,10 @@ it is broken down.
                     handler: swift
                 swift:
                     type:       swift_mailer
-                    from_email: error@example.com
-                    to_email:   error@example.com
+                    from_email: "error@example.com"
+                    to_email:   "error@example.com"
                     # or list of recipients
-                    # to_email:   [dev1@example.com, dev2@example.com, ...]
+                    # to_email:   ["dev1@example.com", "dev2@example.com", ...]
                     subject:    An Error Occurred!
                     level:      debug
 
@@ -169,8 +169,8 @@ get logged on the server as well as the emails being sent:
                     handler: swift
                 swift:
                     type:       swift_mailer
-                    from_email: error@example.com
-                    to_email:   error@example.com
+                    from_email: "error@example.com"
+                    to_email:   "error@example.com"
                     subject:    An Error Occurred!
                     level:      debug
 

cookbook/symfony1.rst

@@ -331,7 +331,7 @@ used them in your application:
     # some app.yml file from symfony1
     all:
       email:
-        from_address:  foo.bar@example.com
+        from_address: "foo.bar@example.com"
 
 In Symfony2, you can also create arbitrary entries under the ``parameters``
 key of your configuration:
@@ -341,7 +341,7 @@ key of your configuration:
     .. code-block:: yaml
 
         parameters:
-            email.from_address: foo.bar@example.com
+            email.from_address: "foo.bar@example.com"
 
     .. code-block:: xml