DistributedArrays depends on SparseArrays

src/mapreduce.jl does 'import SparseArrays: nnz'.  Without this change, Julia
reports an error on 'using DistributedArrays' about the SparseArrays dependency.

Author: samtkaplan

Project.toml

@@ -8,15 +8,15 @@ LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 Primes = "27ebfcd6-29c5-5fa9-bf4b-fb8fc14df3ae"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Serialization = "9e88b42a-f829-5b0c-bbe9-9e923198166b"
+SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
 
 [compat]
 julia = ">= 1.0"
 
 [extras]
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
-SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 SpecialFunctions = "276daf66-3868-5448-9aa4-cd146d93841b"
 
 [targets]
-test = ["Test", "SparseArrays", "SpecialFunctions"]
+test = ["Test", "SpecialFunctions"]