Update for compat with chainable method overwriting

[joshperry]

No description provided.

[domenic]

Tests? What does this fix?

[joshperry]

I didn't change or add functionality, I assumed the existing tests would suffice to ensure there was no change in that regard. I am happy to write some if you feel there is a need.

This fixes the code calling addChainableMethod to overwrite existing methods when chai has overwriteChainableMethod for that purpose. This makes it difficult to manage reentrancy in other plugins that also need to overwrite existing chainable methods.

Also, detecting chainable methods by calling the getters in a try/catch to see if they return a function is error prone if you don't know the preconditions that the getter expects. This instead looks at the chainable method registry that chai keeps.

[domenic]

If there's no change or add to functionality, then there's no reason to merge this. It sounds like there are changes, from your description; there need to be tests for that then.

[domenic]

Ping. Would love tests on this. I noticed from the referenced issue you seem to think I don't like you and am dead-set against this? I can assure you that's not the case.

[domenic]

Superceded by #94, which included tests.