Update README with IAM options.

README.md

@@ -30,13 +30,15 @@ DATABASES = {
         "ENGINE": "django_s3_sqlite",
         "NAME": "sqlite.db",
         "BUCKET": "your-db-bucket",
+	"AWS_S3_ACCESS_KEY": "AKIA0000000000000000",  # optional, to lock down your S3 bucket to an IAM user
+	"AWS_S3_ACCESS_SECRET": "9tIZfakefakefakefakeT9Q6LD6jB5UyofakeISN",  # optional, to lock down your S3 bucket to an IAM user
     }
 }
 ```
 
 Newer versions of Django (v2.1+) require a newer version of SQLite (3.8.3+) than is available on AWS Lambda instances (3.7.17).
 
-**Because of this, you will need to download the provided `_sqlite3.so` for your Python version (available in the `shared-objects` directory of this repository) and put it at the root of your Django project.** Note that only the Python 3.6 and 3.8 runtimes are supported at this time. These shared object files contain a compiled binary static build of SQLite 3.30.1 that can be used with the corresponding version of Python. We hope this will soon be available via [Lambda Packages](https://github.com/Miserlou/lambda-packages), but for now, you will also need to add this line to your Zappa JSON settings file in each environment:
+**Because of this, you will need to download the provided `_sqlite3.so` for your Python version (available in the `shared-objects` directory of this repository) and put it at the root of your Django project.** Note that only the Python 3.6 and 3.8 runtimes are supported at this time. These shared object files contain a compiled binary static build of SQLite 3.30.1 that can be used with the corresponding version of Python. You will also need to add this line to your Zappa JSON settings file in each environment:
 
 ```
 "use_precompiled_packages": false,