Updated README.md

Updated readme to work with the current codebase, as per issue #3.

Author: SWZ

README.md

@@ -4,13 +4,13 @@ Requires Python 3.6.x or Python 3.7
 git clone https://github.com/common-workflow-language/cwl-utils.git
 virtualenv -p python3.6 venv3.6
 source venv3.6/bin/activate
-pip install cwl-utils/docker_cache_pull/requirements.txt
-python docker_cache_pull/docker-extract.py path_to_my_workflow.cwl
+pip install cwl-utils
+python docker-extract.py path_to_my_workflow.cwl
 ```
 
 to regenerate install `schema_salad` package and run:
 
 ```
 schema-salad-tool --codegen python \
     https://raw.githubusercontent.com/common-workflow-language/common-workflow-language/master/v1.0/CommonWorkflowLanguage.yml
-```
+```