Merge pull request #1 from chebfun/development

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Merge branch 'development' into fix-singfun-exponents
Testing for division as differentiation and powers

Codifying previously concerning issues with rdivide.
Tweaking tests for rdivide@singfun from DG.
Merge pull request #1040 from chebfun/fix-singfun-exponents

Fix singfun exponents