Handle tweet citations

[hubgit]

Suggested markup:

<ref id="ref-38">
  <label>Zaman (2014e)</label>
  <element-citation publication-type="tweet">
    <person-group person-group-type="author">
      <name-alternatives>
        <name>
          <surname>Zaman</surname>
          <given-names>L</given-names>
          <!--<suffix>(@LuisZaman)</suffix>-->
        </name>
        <string-name content-type="twitter-username">LuisZaman</string-name>
      </name-alternatives>
    </person-group>
    <year iso-8601-date="2014">2014e</year>
    <date date-type="pub" iso-8601-date="2014-02-01T14:50">2:50 PM - 1 Feb 2014</date>
    <article-title>Surface sterilized PLA that was “snapped” to expose fresh filament not growing in LB @ryneches @runforsushi</article-title>
    <uri>https://twitter.com/LuisZaman/status/429748626449903618</uri>
  </element-citation>
</ref>

[hubgit]

The MLA's "How to cite a tweet" style guide has been taken down; more examples of output needed.

[hubgit]

Possibilities:

• Use <name-alternatives> for the username, instead of <suffix>.
• Put the text of the tweet in double quotes, as the title.
• Add <month> and <day> for the publication date.
• Use the shortened t.co URL.

[hubgit]

Use PHP's date function to output the date in a specific format?