[Ch6Nb03] Added missing functions and missing files.

1.	Added  ‘if torch.cuda.is_available()’ to check if we are using gpu.
2.	Added a try except block to upload files to colab.
3.	Added ‘get_data’ and ‘get_data2’ functions as they were missing.
4.	 Fixed path for windows and colab.
5.	‘load_atis’ and ‘load_data’ functions were missing, so added it.
6.	‘atis.test.pkl’ and ‘atis.train.pkl’ files were missing, so added these files. 
7.	Added a if condition for using ‘model.cuda()’ only when we are using gpu.

Author: KUMAR-APURVA