update readme

README.md

@@ -8,7 +8,7 @@ generate.py is a python program that generates a vagrant source file from a defi
 ### Usage:
 1. Clone the project.
 2. Navigate to the project folder.
-3. Type `$ python generate.py {yaml_file.yaml} > Vagrantfile`. There is a test yaml file in the repository called test.yaml.
+3. Type `$ python generate.py yaml_file.yaml > Vagrantfile`. There is a test yaml file in the repository called test.yaml.
 4. Run `$ vagrant up`
 
 ### Implemented attribute types: