Add user conduit API method

Summary:
(1) Change .arcconfig file to point to our version of phabricator

(2) Modified yesnault/phabricator to point to our git repo (https://github.com/ygrei/phabricator.git) which is a fork of the main one.  Also installed emacs-nox.  Note, export TERM=xterm to get xterm to work

(3) After adding the file.  Run arc liberate to link the php files

Test Plan:
Because I'm a mac user

http://192.168.59.103:8081/conduit

Add a user using the web API.  Then try adding again.  Verify created first time, exception thrown the second

Reviewers: ortutay

Reviewed By: ortutay

Differential Revision: http://ec2-54-69-108-116.us-west-2.compute.amazonaws.com/D30