Upgrade jsonschema (#229)

* Upgrade to jsonschema 4 * Upgrade to jsonschema 4 Closes #228

Author: bcb

setup.py

@@ -27,7 +27,7 @@
  ],
  },
  include_package_data=True,
- install_requires=["jsonschema<4", "oslash<1"],
+ install_requires=["jsonschema<5", "oslash<1"],
  license="MIT",
  long_description=README,
  long_description_content_type="text/markdown",