More informative messages when index out of bound

[fzyzcjy]

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Hi thanks for the lib! When I made a bug and access index out of bound (e.g. arr.slice(s![a..b, c..d])), I see:

Slice begin 16744 is past end of axis of length 184

I would appreciate it if it could be a bit more informative, such as:

Slice begin 16744 is past end of axis of length 184 (array size: 1234x184; slice arg: 123x16744)

Then, programmers can debug the problem quicker - at least we know which axis goes wrong.