v1.2.0

SpecialFunctions v1.2.0

Diff since v1.1.0

Closed issues:

• expintx function — exponentially scaled expint (#249)
• cancellation error in expint for near-integer order and small |z| (#276)
• erfcinv does not support BigFloat (#277)

Merged pull requests:

• Add differentiation rules from ChainRules (#238) (@devmotion)
• Add exponentially scaled exponential integral (expintx) (#270) (@augustt198)
• upper incomplete gamma function Γ(a,z) (#271) (@stevengj)
• bigfloat erfinv and erfcinv (#278) (@stevengj)
• fix spurious domainerror for expint(3.2, 1.3) (#280) (@stevengj)
• expint: series around gamma poles (#281) (@augustt198)