Steps:
1. Download Penn Treebank dataset. It can be found [here](www.fit.vutbr.cz/~imikolov/rnnlm/simple-examples.tgz)

2. Unpack the folder "simple-examples/data/" into "~/lstm_languageModel/data/ptb/raw/"

3. Run the preprocessing script: python preprocess_ptb.py



