README.md in carrierwave-base64-2.3.5 vs README.md in carrierwave-base64-2.4.0

@@ -6,11 +6,11 @@
 
 Upload files encoded as base64 to carrierwave.
 
 This small gem can be useful for API's that interact with mobile devices.
 
-As of version 2.3.0, this gem requires Ruby 2.0 or higher
+This gem requires Ruby 2.0 or higher.
 
 ## Installation
 
 Add the gem to your Gemfile:
 
@@ -32,21 +32,31 @@
 mount_base64_uploader :image, ImageUploader
 ```
 
 Now you can also upload files by passing an encoded base64 string to the attribute.
 
+## Upload file extension
+
+The file extension for the uploaded base64 string is identified automatically using the [mime-types](https://github.com/mime-types/ruby-mime-types/) gem and `content_type` from the uploaded string.
+
+If the required MIME type is not registered, you can add it, using [MIME::Types#add](http://www.rubydoc.info/gems/mime-types/MIME/Types#add-class_method).
+
 ## Setting the file name
 
-To set the file name for the uploaded files, use the `:file_name` option (without extention):
+You can set the `file_name` option to a lambda, that will return a filename without an extension, using the model instance:
 
 ```ruby
-mount_base64_uploader :image, ImageUploader, file_name: 'userpic'
+mount_base64_uploader :image, ImageUploader, file_name: -> (u) { u.username }
 ```
 
-You can also pass a Proc for the file-name to allow dynamic filenames.
+**[DEPRECATED: Settings this option to a string is deprecated, if you still want to set the filename to a fixed string, wrap it in a Proc]** To set the file name for the uploaded files, use the `:file_name` option (without extention):
 
 ```ruby
-mount_base64_uploader :image, ImageUploader, file_name: -> { "file-#{DateTime.now.to_i}" }
+# Deprecated way:
+mount_base64_uploader :image, ImageUploader, file_name: 'userpic'
+
+# New way
+mount_base64_uploader :image, ImageUploader, file_name: -> { 'userpic' }
 ```
 
 ## Data format
 
 The string with the encoded data, should be prefixed with Data URI scheme format: