test_ops: do not lower precision in conversion to Torch tensor (#681)
test_ops: do not lower precision in conversion to Torch tensor (#681)

* test_ops: do not lower precision in conversion to Torch tensor

float64 test values close to zero were rounded by conversion to a
float32 Torch tensor, resuling in mismatches between Thinc and Torch
gradients. This change prevents the loss in precision.

* test_ops: compare arrays on same device in Torch comparison

* test_maxout: compare arrays with same precision
explosion/thinc,explosion/thinc,explosion/thinc,explosion/thinc