Made changes so that batching works for json response

[krototype]

Summary

Updated the type of body that was passed to Response object, so that it works fine for the returned json in case of Batching.

Motivation

Explain the motivation for making this change. What existing problem does the pull request solve?
The BatchResponseContent was not sending the Response body in the correct format for json response type.

Fixes #204

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.