package sharedCredentials provides access to the aws shared credentials file.
It will look for "AWS_SHARED_CREDENTIALS_FILE" env variable.
If the env value is empty will default to current user's home directory.
Linux/OSX: "$HOME/.aws/credentials"
Windows: "%USERPROFILE%\.aws\credentials"
Store function updates the shared credentials with the specified values:
* If the shared credentials file does not exist, it will be created. Any parent directories will also be created.
* If the section to update does not exist, it will be created.