v0.9.14

ApproxFunBase v0.9.14

Diff since v0.9.13

Merged pull requests:

• Backport: Improve type-inference in multiplying with TimesOperator (#588) (@jishnub)
• Delete AFOP test directory (#589) (@jishnub)
• isnegative in intpow (#590) (@jishnub)
• backport: isnegative in intpow (#591) (@jishnub)
• Don't treat ConstantOperator as a zeroop (#592) (@jishnub)
• Backport: Don't treat ConstantOperator as a zeroop (#593) (@jishnub)
• Restore skip CI (#594) (@jishnub)