Updated GraphRequest.ts to handle .count() when no parameter is specified

Summary

When the query parameter .count() didn't have any parameter passed, it used to give an error.
So adding the default value as false for this case (this is according to the graph behavior).

Closing issues

#241

Fixes #241

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.