torchscript, cpu and gpu support

[horheynm]

Torchscript integration

Example

model = "path_to_dot_pt" or nn_module or torchscipt_model
device = "cpu" or "cuda"
engine = TorchScriptEngine(model, device=device)
inp = [numpy.random.rand(1, 3, 224, 224).astype(numpy.float32)]
out = engine(inp)

[bfineran]

LGTM pending comments - additionally, let's update PR description to include scope of feature as well as example snippet

future work should add zoo support