Refactor: name modules (#548)

* refactor: rename some modules

* add deprecation warnings

* fix paths

pytorch_lightning/root_module/grads.py

@@ -1,29 +0,0 @@
-"""
-Module to describe gradients
-"""
-
-from torch import nn
-
-
-class GradInformation(nn.Module):
-
-    def grad_norm(self, norm_type):
-        results = {}
-        total_norm = 0
-        for i, p in enumerate(self.parameters()):
-            if p.requires_grad:
-                try:
-                    param_norm = p.grad.data.norm(norm_type)
-                    total_norm += param_norm ** norm_type
-                    norm = param_norm ** (1 / norm_type)
-
-                    grad = round(norm.data.cpu().numpy().flatten()[0], 3)
-                    results['grad_{}_norm_{}'.format(norm_type, i)] = grad
-                except Exception:
-                    # this param had no grad
-                    pass
-
-        total_norm = total_norm ** (1. / norm_type)
-        grad = round(total_norm.data.cpu().numpy().flatten()[0], 3)
-        results['grad_{}_norm_total'.format(norm_type)] = grad
-        return results