The Server Cache administration widget had some precision errors when

running on Python 3, due to differences in division. We now explicitly

opt into the division future, for Python 2.7, and explciitly format

the numbers in all cases. This gives us the same results as in Review

Board 3, with the addition of 2 digits of precision we now provide for

the percentages.
The lines in the widget are also now left-aligned. Due to a regression,

they were center-aligned in 4.0.0.

Tested the widget on both Python 2.7 and 3.x, ensuring the appearance was

correct and the same between both.