Rework the list view

Based on the work from: Lukas Brabec <lukas.sparrow@gmail.com>
at: https://fedorahosted.org/fedocal/ticket/129
Do not show the location if there are None
Rename the event CSS class to event_blue
Add the event css class to the `show more` link

This way the information pop-up will work on both the blue box with the
meeting name and the `show more` link in its description
If there is no text to convert via markdown, return an empty string
Add a new jinja filter wrapping the first three line of text and converting them via markdown
Only show part of the meeting's description in the list view
Reduce the number of lines shown about the meeting's description
Adjust the unit-tests for the new presentation of the list view
Merge pull request #142 from fedora-infra/list_view

List view