Test "lots of gpio refs can be created" is failing

Reduce count to 100.  See if it is a timing issue.

Author: mdsebald

test/circuits_gpio_test.exs

@@ -69,6 +69,9 @@ defmodule Circuits.GPIOTest do
       send(me, {:done, length(x)})
     end)
 
+    # Wait a tehth of a second to allow spawned task to complete
+    Process.sleep(100)
+
     assert_receive {:done, ^count}
 
     # Wait a fraction of a second to allow GC to run since there's