Fixed calculation logic, adjusted css

Changes:
- Fixed it so we calculate averages outside of the loop. (Instead of
calculating it every iteration)
- Adjusted CSS.
- Removed "Character" text from Ranked tab for space.

Resolved:
- https://github.com/edwardsdl/dominance-factor-bookmarklet/issues/3
- https://github.com/edwardsdl/dominance-factor-bookmarklet/issues/1