Generate parser from cwltool extensions

This commit fixes #309 by generating the Python CWL parsers directly
from the `codegen` branch of cwltool, including all the cwltool
extensions in the parsers logic.

Author: GlassOfWhiskey

Diff for: README.rst

@@ -152,13 +152,13 @@ Regenerate parsers
 To regenerate install the ``schema_salad`` package and run:
 
 ``cwl_utils/parser/cwl_v1_0.py`` was created via
-``schema-salad-tool --codegen python https://github.com/common-workflow-language/common-workflow-language/raw/codegen/v1.0/CommonWorkflowLanguage.yml --codegen-parser-info "org.w3id.cwl.v1_0" > cwl_utils/parser/cwl_v1_0.py``
+``schema-salad-tool --codegen python https://github.com/common-workflow-language/cwltool/raw/codegen/cwltool/extensions.yml --codegen-parser-info "org.w3id.cwl.v1_0" > cwl_utils/parser/cwl_v1_0.py``
 
 ``cwl_utils/parser/cwl_v1_1.py`` was created via
-``schema-salad-tool --codegen python https://github.com/common-workflow-language/cwl-v1.1/raw/codegen/CommonWorkflowLanguage.yml --codegen-parser-info "org.w3id.cwl.v1_1" > cwl_utils/parser/cwl_v1_1.py``
+``schema-salad-tool --codegen python https://github.com/common-workflow-language/cwltool/raw/codegen/cwltool/extensions-v1.1.yml --codegen-parser-info "org.w3id.cwl.v1_1" > cwl_utils/parser/cwl_v1_1.py``
 
 ``cwl_utils/parser/cwl_v1_2.py`` was created via
-``schema-salad-tool --codegen python https://github.com/common-workflow-language/cwl-v1.2/raw/1.2.1_proposed/CommonWorkflowLanguage.yml --codegen-parser-info "org.w3id.cwl.v1_2" > cwl_utils/parser/cwl_v1_2.py``
+``schema-salad-tool --codegen python https://github.com/common-workflow-language/cwltool/raw/codegen/cwltool/extensions-v1.2.yml --codegen-parser-info "org.w3id.cwl.v1_2" > cwl_utils/parser/cwl_v1_2.py``
 
 Release
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