Truncate entry content with CSS

[facundoolano]

I currently have a couple of template filters to truncate the entry content (full/text view and compact/pinned view) in Python. This is because I couldn't get the HTML and CSS to show ellipsis on overflow. Ideally containers should be fixed in size (e.g. the height of the image preview) and the CSS would adjust the text to take advantage of the available space, instead of the current solution which isn't consistent and leaves some blanks.