Bump SpecialFunctions to v2 (#66)

Let's see if the CI passes with this

Author: jishnub

Project.toml

@@ -17,5 +17,5 @@ Combinatorics = "0.7.0, 1"
 Distributions = "0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25"
 FastGaussQuadrature = "0.3, 0.4"
 GSL = "0.4, 1"
-SpecialFunctions = "0.7, 1"
+SpecialFunctions = "0.7, 1, 2"
 julia = "0.7, 1"