Add language to paste.info, and show it in Pxxx responses from phabot.

Summary:
Now that we store language with pastes, we can include this in Conduit.

Test Plan:
Tried it on a paste with a blank language, and one with a specified language.

16:14:50 <@CodeBlock> P1
16:14:51 <@codeblock-phabot> P1: http://phabricator.local/P1 - test.php
16:15:05 <@CodeBlock> P43
16:15:06 <@codeblock-phabot> P43: http://phabricator.local/P43 - sadoijfoisaf (php)

Reviewers:
epriestley, Ttech

CC:

Differential Revision: 616