Added more upgrading detail to the readme (#316)

Author: GrahamCampbell

README.md

@@ -17,11 +17,17 @@ New in Version 3 is first-class support for multiline variables
 ([#301](https://github.com/vlucas/phpdotenv/pull/301)) and much more
 flexibility in terms of which parts of the environment we try to read and
 modify ([#300](https://github.com/vlucas/phpdotenv/pull/300)). Consequently,
-you will need to replace any occurences of `new Dotenv(...)` with
+you will need to replace any occurrences of `new Dotenv(...)` with
 `Dotenv::create(...)`, since our new native constructor takes loader instance
 now, so that it can be truly customized if required. Finally, one should note
-that starting from V3, the loader will no longer be trimming values
-([#302](https://github.com/vlucas/phpdotenv/pull/302)).
+the loader will no longer be trimming values
+([#302](https://github.com/vlucas/phpdotenv/pull/302)), moreover
+`Loader::load()` and its callers now return an associative array of the
+variables loaded with their values, rather than an array of raw lines from the
+environment file ([#306](https://github.com/vlucas/phpdotenv/pull/306)).
+
+For more details, please see the
+[release notes](https://github.com/vlucas/phpdotenv/releases/tag/v3.0.0).
 
 
 Why .env?