Guarantee ordering of events and entitites

[brandomr]

This pull request contains minor updates to Main.py intended to preserve ordering or critical dictionaries when sent for Causality Detection. Also, this includes sorting keys of dictionaries prior to iterating through them to preserve span ordering as it appears in the text submitted to SOFIA.

Until Python 3.6 there was no guarantee of ordering in dictionaries. Python 3.6 and beyond, insertion ordering is guaranteed. Take this example:

sample = {}
sample['susan'] = 1
sample['bob'] = 50
sample['jim'] = 100

In Python 2, if we ask for sample.keys() we will be returned keys in arbitrary order. For example this could return ['bob', 'susan', 'jim'].

In Python 3 sample.keys() will return the keys in insertion order which must be: ['susan', 'bob', 'jim']

Since the key order is relied on by CausalityDetection.py, it is preferable to use OrderedDict to ensure compatibility with Python 2 and Python 3.