Fixed failing test

I'm a bit stomped by this test failure as it didn't show up in the CI of PR:
#34

Furthermore, the same issue existed as far back as
#25

I tried to see whether this was introduced in one of the minor
versions of Julia 0.5.  But running the test now locally fails for all
0.5.0, 0.5.1 and 0.5.2.

So, not sure what changed.

src/SimpleTraits.jl

@@ -153,12 +153,14 @@ macro traitimpl(tr)
                 $fnhead = $trname{$(paras...)}
                 VERSION < v"0.6-" && ($isfnhead = true) # Add the istrait definition as otherwise
                                                         # method-caching can be an issue.
+                nothing
             end
         else
             return quote
                 $fnhead = Not{$trname{$(paras...)}}
                 VERSION < v"0.6-" && ($isfnhead = false) # Add the istrait definition as otherwise
                                                          # method-caching can be an issue.
+                nothing
             end
         end
     elseif tr.head==:call
@@ -177,12 +179,14 @@ macro traitimpl(tr)
                                P1 = $P1
                                return $fn($(P2...)) ? :($Tr{$(P1...)}) : :(Not{$Tr{$(P1...)}})
                            end
+                           nothing
                        end)
         else
             return esc(quote
                            function SimpleTraits.trait{$(P1...)}(::Type{$Tr{$(P1...)}})
                                return $fn($(P2...)) ? $Tr{$(P1...)} : Not{$Tr{$(P1...)}}
                            end
+                           nothing
                        end)
         end
     else

test/base-traits.jl

@@ -30,6 +30,6 @@ type T9867 end
 @test istrait(IsCallable{T9867})
 
 @test istrait(IsIterator{Array})
-@test !istrait(IsIterator{Cmd})
+@test !istrait(IsIterator{Symbol})
 @test istrait(IsIterator{Base.UnitRange{Int}})
 @test istrait(IsIterator{Base.UnitRange})