v1.8.4

SpecialFunctions v1.8.4

Diff since v1.8.3

Closed issues:

• incomplete beta (beta_inc) function fails (#334)

Merged pull requests:

• Fix a bug in coeff2 and add a test (#391) (@andreasnoack)
• Underflow without erroring in beta_inc (#392) (@andreasnoack)
• Avoid NaN in beta_inc_inv when p=q=1. (#393) (@andreasnoack)
• More bugfixes to backport (#394) (@andreasnoack)