Redegisn tests for the constructor
Implement the constructor
Fix test module declarations
Add a test for getter for slack helper
Implement SlackHelper getter
Change test values
Refine a test code
Add a test for Statbot#send
Make method name clarify
Add a reference
Remove a test for SlackHelper
Add a test case
Add tests for sending a message
Rename an incoming hook URI getter method
Fix test bugs
Improve a Statbot#say method