Raise exceptions for known errors

[Sparks29032]

• On squeeze, if the polynomial squeeze causes the function grid to be non-strictly-increasing, an error is thrown. Let's wrap the CubicSpline call in morphsqueeze.py with a try catch to throw a custom warning to the user.
• If the grids of the morphed and target functions after the first iterations are too far separated (e.g. there is no overlap, or only one point overlap), then it is possible for the number of parameters to be smaller than the number of points we are regressing to fit over. This causes an error. In refine.py in the _residual function, let's throw a custom error to the user if len(rvec) < len(pvals).

[sbillinge]

@Sparks29032 @ycexiao can this be closed?

[ycexiao]

The situation described in the first unchecked item will be addressed differently in #256.

[sbillinge]

Thanks @ycexiao . Per your comment I am closing this as completed or moved to #256