[nailer]

Hi, everybody!
Thanks to KevinH, this plugin is useful, but I have some troubles with its work.
So follow bit of code was handled by plugin:

Spoiler:

<dc:date opf:event="modification">2015-07-10</dc:date>
<meta property="media:duration" refines="#s001">0:13:31.389</meta>
<meta property="media:duration" refines="#s002">0:15:14.939</meta>
<meta property="media:duration">0:28:46.328</meta>
<meta property="media:narrator">nailer</meta>
<meta property="media:active-class">-epub-media-overlay-active</meta>

result:

Spoiler:

<meta property="media:duration" refines="#s001" />
<meta property="media:duration" refines="#s002" />
<meta property="media:duration" />
<meta property="media:narrator" />
<meta property="media:active-class" />
<meta property="dcterms:modified">2015-07-09T17:38:52Z</meta>

Windows 8-x64, Python 3.4.3, Sigil 0.8.7 v5.4.0, ePub3-itizer_v031, (epubcheck-3.0.1)
If I convert the epub2 by hand the epub3 file was validated successfully:
"Validating against EPUB version 3.0
No errors or warnings detected."