Copy HostSendNode x value to work with new Nengo

We used to do this copy in Nengo, now we don't, so need to copy here.

nengo_loihi/builder/inputs.py

@@ -19,7 +19,7 @@ def __init__(self, dimensions, label=Default, check_output=False):
 
     def update(self, t, x):
         assert len(self.queue) == 0 or t > self.queue[-1][0]
-        self.queue.append((t, x))
+        self.queue.append((t, x.copy()))
 
 
 class HostReceiveNode(Node):
@@ -42,6 +42,7 @@ def update(self, t):
         return x
 
     def receive(self, t, x):
+        # we assume that x will not be mutated (i.e. we do not need to copy)
         self.queue.append((t, x))