Update to node-expat 2.0.0

[justinrainbow]

The 2.0.0 version of node-expat bundles the libexpat dependency (xmppo/node-expat#48) which makes it easier for both Windows / Unix users to get node-expat installed.

Here's a link to the full diff between node-expat v1.6.1 and v2.0.0 - xmppo/node-expat@v1.6.1...v2.0.0

[powdahound]

Last time I tried this there were some incompatibilities. Did you verify that this works?

[justinrainbow]

Yup, I've been running it with the latest version of Hubot and haven't run in to any issues yet.

[powdahound]

Are you on Heroku? It was failing to build there previously; #46

[laurentkempe]

I just installed it on my Windows 8 64bits machine running node v0.10.5 and could connect hubot to our hipchat rooms without any issue!

With v1.6.1 you get a compilation error as the one discussed there xmppjs/ltx#16

[rbergman]

I'm not sure why we had node-expat in the hubot-hipchat package.json, but it doesn't seem to be required there any more and has therefore been removed. Both ltx and node-xmpp declare their node-expat dependencies such that they result in 2.0.0 being brought in with a fresh hubot-hipchat installation now. Since they are the only hubot-hipchat dependencies that in turn require node-expat, it looks like this issue is obsolete.