Include category on submission detail screen

[aguywithanidea]

Nothing on this screen tells me I'm reading "micro-fiction"

[aguywithanidea]

The category is available in the XML object:

<submission>
        <id>20961</id>
        <title>Defiance</title>
        <submission_date>2017-03-21</submission_date>
        <days_pending>754</days_pending>
        <category>
            <name>Poetry</name>
            <id>87</id>
        </category>

[aguywithanidea]

This will be fixed by #125. Marking as done and will close when plugin upgrade is released.