Need word2vec and Glove modules

[suriyadeepan]

Most reading comprehension and question answering models require embedding initialization with Glove/word2vec. We need a module that provides an embedding matrix, given a word2idx/idx2word dictionary or just a dictionary that can provide embedding given a word as key.

We also need a mapping between the dimensions of embeddings to file names of pretrained embeddings. For example glove.6B.100d.txt contains 100 dimensional embeddings.