special characters are not allowed

When running against https://raw.githubusercontent.com/docusign/OpenAPI-Specifications/master/esignature.rest.swagger-v2.1.json (Note this was as of today at this time, I've attached a file which is a copy of the state of this file as of today)
```openapi2jsonschema https://raw.githubusercontent.com/docusign/OpenAPI-Specifications/master/esignature.rest.swagger-v2.1.json```

Fails with
```
visch@visch-ubuntu:~/git/tap-docusign$ openapi2jsonschema https://raw.githubusercontent.com/docusign/OpenAPI-Specifications/master/esignature.rest.swagger-v2.1.json
Downloading schema
Parsing schema
Traceback (most recent call last):
File "/home/visch/.local/bin/openapi2jsonschema", line 8, in
sys.exit(default())
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/click/core.py", line 829, in __call__
return self.main(*args, **kwargs)
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/click/core.py", line 782, in main
rv = self.invoke(ctx)
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/click/core.py", line 1066, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/click/core.py", line 610, in invoke return callback(*args, **kwargs)
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/openapi2jsonschema/command.py", line 68, in default
data = yaml.load(response.read(), Loader=yaml.SafeLoader)
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/yaml/__init__.py", line 112, in load
loader = Loader(stream)
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/yaml/loader.py", line 34, in __init__
Reader.__init__(self, stream)
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/yaml/reader.py", line 79, in __init__
self.determine_encoding()
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/yaml/reader.py", line 135, in determine_encoding
self.update(1)
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/yaml/reader.py", line 169, in update
self.check_printable(data)
File "/home/visch/.local/pipx/venvs/openapi2jsonschema/lib/python3.9/site-packages/yaml/reader.py", line 143, in check_printable
raise ReaderError(self.name, position, ord(character),
yaml.reader.ReaderError: unacceptable character #x0080: special characters are not allowed
```

[esignature.rest.swagger-v2.1.txt](https://github.com/instrumenta/openapi2jsonschema/files/8856052/esignature.rest.swagger-v2.1.txt)