Fix: Recipient tooltip not visible when details are hidden.

When message details are hidden, if user hovers on a recipient contact
name the tooltip is not visible.
Actually sometimes one can see a tiny 1-pixel horizontal line, that is
the upper border of the tooltip, hidden behind other parts of the UI.
Refactor: reordered rules in conversation.css

Rules related to message header and recipients have been placed closer
together. Rule related to menu arrow has been placed closer to option
rule.
Merge pull request #799 from BrainCrumbz/master

Fix: Recipient tooltip not visible when details are hidden. …