Adjust width of identity icon, adjust gradients on mac

-Add a min-width to the identity icon and search selector so they are not shrunk at small window sizes.
-adjust the color of the navbar gradient
-add a gradient to the tabstrip so that it is not just using the background color of the body

These changes are also included in #110 
Starting in firefox 34, the gradient was changed on osx yosemite to use <code> #F1F1F1 </code>, and it appeared from the url and search input boxes that the goal was to match yosemite. However, there is not a big difference between the two, and either one would work. Which one would you like me to use?