add rels.py: extract mention and retweet relations between users
build nodes and links based on mentions, with counts
produce json output like http://bl.ocks.org/mbostock/4062045
produce json output like http://bl.ocks.org/mbostock/4062045
Merge branch 'rels' of https://github.com/pbinkley/twarc into rels
rels.py output works with D3 example
proper output for rels.py
added directed graph version
refactored rels.py and directed.py to generate self-sufficient html
handle -m parameter to choose mentions or retweets
removed rels.py and rels.html - they were drafts of directed.py
changed -m to --mode for consistency with other utils
updated README.md and .gitignore for addition of utils/directed.py