v3.0 Release (#725)

* initial commit

* remove yolov3-spp from test.py study

* update study --img range

* update mAP

* cleanup and speed updates

* update README plot

utils/activations.py

@@ -10,12 +10,6 @@ class Swish(nn.Module):  #
         return x * torch.sigmoid(x)
 
 
-class HardSwish(nn.Module):
-    @staticmethod
-    def forward(x):
-        return x * F.hardtanh(x + 3, 0., 6., True) / 6.
-
-
 class MemoryEfficientSwish(nn.Module):
     class F(torch.autograd.Function):
         @staticmethod