Adds support for msg_id & thread_id

[Xotl]

Fixes issue #189, #191 & #169.

[jtliao]

Can you pass in the new params directly instead? The current change may be a bit misleading, and we can pass in default params for threadId and msgId to get around the backwards compatibility issue

[jtliao]

have msgId and threadId as parameters with default values

[Xotl]

Having Wit.message() to receive more params it's not maintainable. It just increases the Cyclomatic complexity.

A good approach to solve this problem is to have an object with the params we want.

See issue #189.

[jtliao]

I would argue the complexity is higher if a single argument takes different forms. I'm not sure how adding two params with default values makes thing not maintainable.

[Xotl]

if we pass a single object we can just iterate over the properties of such object instead of adding more if's.

Regarding the maintainability, what will happen if suddenly the /messages endpoint deprecates one field?, let's say verbose gets deprecated... you will be passing null always for that parameter even though it's no longer used.

[Xotl]

Updated the PR to show what the implementation look like