README.md in imgurapi-3.0.2 vs README.md in imgurapi-3.1.0

@@ -44,11 +44,11 @@
 
 ## Usage and overview
 
 Create a session object to communicate to Imgur.
 ```ruby
-imgur_session = Imgurapi::Session.new(client_id: 'CLIENT_ID', client_secret: 'CLIENT_SECRET', refresh_token: 'REFRESH_TOKEN')
+imgur_session = Imgurapi::Session.instance(client_id: 'CLIENT_ID', client_secret: 'CLIENT_SECRET', refresh_token: 'REFRESH_TOKEN')
 ```
 
 Your account:
 ```ruby
 account = imgur_session.account.account
@@ -58,13 +58,17 @@
 How many images you have:
 ```ruby
 puts imgur_session.account.image_count
 ```
 
-Upload your first image. Argument can be either a String or a File:
+Upload your first image. Argument can either be a path to a file, a File or a link:
 ```ruby
 image = imgur_session.image.image_upload('portrait.jpg')
+# or
+image = imgur_session.image.image_upload(portrait_file)
+# or
+image = imgur_session.image.image_upload('http://domain.tld/portrait.jpg')
 ```
 
 image is now an instance of Imgurapi::Image, a convenient way to manage all the attributes of your image (at least more convenient than a multilevel dictionary):
 ```ruby
 name = nil
@@ -113,10 +117,11 @@
 imgur_session.image.image_delete('xyzzy')
 ```
 It will return true if succeeded, false otherwise.
 
 ## Available endpoints
+
 Not all the endpoints available at https://api.imgur.com/ have been implemented.
 Feel free to suggest or pull request your needs.
 
 The API methods have been named following Imgur's endpoints, for easy mental mapping.
 Although I consider this is clearer, in the future it may change to follow the naming conventions of the official Python API.
@@ -127,5 +132,17 @@
 | Account | account.images | https://api.imgur.com/endpoints/account#images |
 | Account | account.image_count | https://api.imgur.com/endpoints/account#image-count |
 | Image | image.image | https://api.imgur.com/endpoints/image#image |
 | Image | image.image_upload | https://api.imgur.com/endpoints/image#image-upload |
 | Image | image.image_delete | https://api.imgur.com/endpoints/image#image-delete |
+
+## Accessing more than one account at once
+
+Imgur's ACCESS_TOKEN expires after 1 month. When you make an API request, if the ACCESS_TOKEN is invalid, the library will attempt to get a new one via the REFRESH_TOKEN. This new ACCESS_TOKEN will live with the instance of the library, if you instantiated the Imgurapi::Session with `.new`. So if you instantiate a new session, the token will be requested again.
+
+Given requesting a new ACCESS_TOKEN on every API call is slow, the recommended way of using Imgurapi::Session is via `.instance`, not `.new` so it requests a fresh ACCESS_TOKEN only once, which will be stored at class level, reducing optimally the number of token requests.
+
+This approach is not feasible if you want to handle several Imgur accounts at once.
+
+In short:
+ - instantiate Imgurapi::Session via `.instance` if you manage 1 account
+ - instantiate Imgurapi::Session via `.new` if you manage 2 or more accounts