v1.6.0

SpecialFunctions v1.6.0

Diff since v1.5.1

Closed issues:

• Derivatives of exponential integrals (#321)
• Returning a tuple will affect performance (#330)
• logbeta is type-unstable (#331)

Merged pull requests:

• Fix logabsbeta for BigFloat (#325) (@devmotion)
• Update Drone CI setup (#326) (@giordano)
• Add differentials for exponential integrals (#328) (@devmotion)
• fix type-instability of logabsbeta (#332) (@stevengj)
• Support ChainRulesCore v1 (#335) (@oxinabox)