add example of self-supervised SimCLR training - V2 (#50)

* add example of self-supervised SimCLR training

* simclr v2, replace nvidia dali dataloader

* updated

* sync to latest code writing style

* sync to latest code writing style and modify README

* detail README & standardize dataset path

examples/simclr_cifar10_data_parallel/models/linear_eval.py

@@ -0,0 +1,19 @@
+import torch
+import torch.nn as nn
+import torch.nn.functional as F
+from .Backbone import backbone
+
+class Linear_eval(nn.Module):
+
+    def __init__(self, model='resnet18', class_num=10, **kwargs):
+        super().__init__()
+        
+        self.backbone = backbone(model, **kwargs)
+        self.backbone.requires_grad_(False)
+        self.fc = nn.Linear(self.backbone.output_dim, class_num)
+        
+    def forward(self, x):
+
+        out = self.backbone(x)
+        out = self.fc(out)
+        return out