Merge pull request #215 from trett/qt5

[qt5] bearermanager
[UrlPreview] Fixed urlpreview.
Merge pull request #217 from trett/qt5

[tabbar] highlighting tabs at unread messages
Merge pull request #216 from nico-izo/qt5

[UrlPreview] Fixed urlpreview.
Turned on -std=c++11 by default
[tabbar] change logic to highlight