Add 'phaste' tool for pastebinning text to Phabricator

Provides the ability to pastebin text on Wikimedia's Phabricator installation
from anywhere in production by running 'phaste' -- e.g.:

    # read from stdin:
    grep xfs /var/log/syslog | phaste

    # read from file:
    phaste /var/log/upstart/service.log

Change-Id: I4705178445e4f1437cb606f92f2108755c095e87
Merge "Add 'phaste' tool for pastebinning text to Phabricator" into production