[BUG] Trend no longer works correctly

[jbogaardt]

Describe the bug
I think a commit flipped start and end in the Triangle.trend method. However, nothing was done to correct the inputs of either the Trend estimator not CapeCod which uses the underlying triangle method, so I believe these are producing inaccurate results. I also think we shouldn't change behavior of existing methods without a formal deprecation. Users will likely have a variety of existing code that relies on the prior approach and they need a lead time to react to this change. I think this needs to be reverted.

Refer to commit efde4a6 for items to be reverted.