Initial commit of the PRA code to github.

This code has been much improved since I ran experiments for the EMNLP 2013
paper.  However, there are settings still available to reproduce those
results, with one exception - I've very recently been changing the way
negative evidence is handled.  To reproduce the paper results, sample from the
negative (unseen, in this code) examples until you have as many negative
examples as positive, instead of just downweighting the negatives until there
is even weight.
Create README.md
Fixed lines in README
Added contact info
Update README.md
Updated README.md
Fixed merge conflict
Starting to switch to maven instead of ant
Added my graphchi-java fork as a dependency
Removing old files
Updated to the lastest PRA code, and it appears to work, with passing tests
Added code coverage to the build
Added a TODO to the readme (mostly just testing something)
Make KbPraDriver more accessible to other code, plus a few clean ups
Merge branch 'master' of https://github.com/matt-gardner/pra
Fixed a couple of bugs
Trying to get a temporary github-hosted mvn repo going
A couple of bug fixes, better handling of negative test instances, and other misc stuff
Updated the README
Made a link better in the README