[yt-dev] call for testing: Orion particle support

[j s oishi]

Hi All Orion Users,

I've updated my pull request (#99,
https://bitbucket.org/yt_analysis/yt/pull-request/99/handle-case-of-orion-datasets-without-star)
to fix Orion particle support for the cases of Star, Sink, and no
particle files. Could some of you please test this code and see if it
works? Once this is done, someone can accept the pull request.

thanks,

J.S.