Drop Logging.jl (#205)

Julia 0.7 is having improved logging capabilities, we can drop
Logging.jl.

test/test_mortar_2d_contact.jl

@@ -5,9 +5,6 @@ using JuliaFEM
 using JuliaFEM.Preprocess
 using JuliaFEM.Testing
 
-using Logging
-Logging.configure(level=DEBUG)
-
 mesh = Mesh()
 add_node!(mesh, 1, [0.0, 0.0])
 add_node!(mesh, 2, [1.0, 0.0])

test/test_problems_elasticity.jl

@@ -46,7 +46,6 @@ using JuliaFEM.Testing
         a = geom[i]
         b = strain[i]
         c = stress[i]
-        debug("$a -> $b -> $c")
         @test isapprox(b, [-1/3, -1/3, 1.0, 0.0, 0.0, 0.0])
         @test isapprox(c, [0.0, 0.0, 288.0, 0.0, 0.0, 0.0])
     end