[PATCH 0 of 1 calendar] Fix Timeperiod adaptation to Icalendar

[Simon Chabot]

Hi List,

    I wrote a small patch that should fix Timeperiod adaptation to Icalendar.

    The issue was that the adapter was not inheriting from the
    `ICalendarableAdapter` and, therefore, some attributs were missing (the
    `component` attribut in that case).

    I have also added a small test, that shows the adapters and the rendering
    are going well.

    It would be nice if someone could review this CS, so that we could release a
    bug fix.


    Best,

Simon Chabot.