Falsey body values are incorrectly failing validation

[AlexDobeck]

OpenAPI version
OpenApi 2 and OpenApi 3

Describe the bug
'false' response bodies are failing validation in OpenApi 2 and OpenApi 3.
nullable responses bodies are failing validation in OpenApi 3

To Reproduce
Steps to reproduce boolean failure:

1. Create a spec with a boolean body response (OpenApi2/OpenApi3)
2. Attempt to validate a 'false' response
3. Notice the validation fails

Steps to reproduce nullable failure:

1. Create a spec with a nullable body response (OpenApi3)
2. Attempt to validate a null response
3. Notice the validation fails

Expected behavior
null and false values should be valid response bodies as allowed by the OpenApi specs

[AlexDobeck]

I have submitted a PR I believe will resolve this issue:
#50

[rwalle61]

Released, I'll let you close

[AlexDobeck]

Excellent, thanks for the fast turn-around.