Fix the output with the latest version of org-mode.

Org-mode had a bug fix, which changed the default mode of opening a
buffer and caused issues when exporting it.  See [1] for details.
Thanks to 邓栓 for reporting it.

[1] http://orgmode.org/cgit.cgi/org-mode.git/commit/?id=44acd000
Fix issues with unicode filenames for posts.

Thanks again to 邓栓for reporting it. Fixes #19.
Use an OrderedDict if available, for the post metadata.
Merge pull request #20 from getnikola/org-plugin-fixes

Couple of fixes for the orgmode plugin