[Firefox] Cosmetic - Icon count misaligned in options menu

[rodalpho]

When the uBlock icon is moved to the Firefox options menu (the 3 lines "hamburger" menu), the blocked count is misaligned below the icon instead of offset inside it.

[gregseth]

In a related manner, the icon count is also misaligned in the icon bar (on Mac OS X only, OS X 10.10.2, Firefox 35.0.1).

[chrisaljoudi]

Dup of #545 (probably).