Do not test zip() on Julia 1.0 as it's unsupported

Author: tkf

test/test_sparse_int_set.jl

@@ -185,6 +185,8 @@ import DataStructures: SparseIntSet
 	    end
 	    @test s1 == 4*24
 	end
-        @test zip() isa Iterators.Zip  # issue 621
+        if VERSION >= v"1.1"
+            @test zip() isa Iterators.Zip  # issue 621
+        end
 
 end