Incorrect Version Requirement

[JakeStevens]

The README states: If you already had a version of PyTorch installed on your system, please verify that the active torch package is at least version 0.1.11

However, my version of PyTorch (0.3.1) >= 0.1.11, but there are compatibility issues. The README should be updated to reflect the actual minimum version supported.

Given that the code uses no_grad, which is introduced in 0.4.0, the minimum version should be 0.4.0