Use @__DIR__ instead of Pkg.dir

this allows installing and loading the package from elsewhere

test/test_elasticity_3d_linear_with_surface_load.jl

@@ -49,7 +49,7 @@ using JuliaFEM.Testing
 end
 
 function solve_rod_model_elasticity(eltype)
-    fn = Pkg.dir("JuliaFEM") * "/test/testdata/rod_short.med"
+    fn = @__DIR__() * "/testdata/rod_short.med"
     mesh = aster_read_mesh(fn, eltype)
     element_sets = join(keys(mesh.element_sets), ", ")
     info("element sets: $element_sets")