CI failed: Inconsistent definition from schema_salad

# Background

Travis CI is failing everyday. That is significant problem as an OSS.

`.cwl` files in CWL repository **are invalid** as being validated by [schema_salad](https://github.com/common-workflow-language/schema_salad). This is because `schema_salad` checks the duplicated keys of dictionary with granting whole cwl as one dictionary.

Obviously CWL requires the same key names to make references between some inputs.

It means `schema_salad`, supposed to be a validator for CWL, doesn't support CWL.

# Suggestion

As an OSS, the health check of software is, per se, a guideline to contribute. I, as a programmer, want to suggest/pull-request following process to make this OSS healthy.

1. **Temporarily** allow duplicated keys in schema_salad to make the status green
2. Keep green developing CWL continuously
3. **In parallel** make more specific validation in schema_salad