No documentation or scripting to download GloVe pretrained embeddings

[zwelz3]

Not a big issue, but it's probably worth a quick update to include either documentation in the readme to download the GloVe pretrained 100B word embeddings, or a curl command to the scripts, otherwise following procedure causes an assertion error that requires traceback to the missing file.

Traceback (most recent call last):
  File "jNERE.py", line 77, in <module>
    parser = learner.jNeRE(words, nertags, rels, w2i, c2i, options)
  File ".../jointRE/jNERE/learner.py", line 58, in __init__
    assert (ext_emb_dim == self.wdims)
AssertionError