v0.13.21

ApproxFun v0.13.21

Diff since v0.13.20

Closed issues:

• Add the option to specify the number of coefficients (#886)

Merged pull requests:

• move fractional calculus to ApproxFunSingularities (#885) (@jishnub)
• Move DualNumbers to an extension (#888) (@jishnub)
• test with Aqua 0.6 (#889) (@jishnub)
• Docs: display operators in repl blocks (#890) (@jishnub)
• re-enable test for bigfloat (#892) (@jishnub)
• change latest to dev in readme (#893) (@jishnub)
• Test on v1.10 (#894) (@jishnub)
• Clean up imports (#895) (@jishnub)