moved env variables to global variables; (#215)

added branch context;
added vocab parallel layers;
moved split_batch from load_batch to tensor parallel embedding layers;
updated gpt model;
updated unit test cases;
fixed few collective communicator bugs

tests/test_layers/test_3d/checks_3d/common.py

@@ -10,6 +10,7 @@ HIDDEN_SIZE = 8
 NUM_CLASSES = 8
 NUM_BLOCKS = 2
 IMG_SIZE = 16
+VOCAB_SIZE = 16
 
 def check_equal(A, B):
     eq = torch.allclose(A, B, rtol=1e-3, atol=1e-2)