Make `bazinga` as optional field by config

[vkatsuba]

sheldon version

0.3.0

OS version

Ubuntu

Description

• Motivation
  Not all users want to see bazinga in response from sheldon. It would be great have configuration for this behavior.
• Proposal
  Add new config option show_bazinga true/false to skip bazinga message from sheldon in response.

Current behavior

The bazinga field in response always provided.

Expected behavior

The bazinga field in response should be configurable.