Dynamically Size Treble Entry Display

[ryanoneill]

The code for the 3 column widths (buffer number, icon, and buffer name) are currently statically sized at 5, 5, and 40 respectively. This was done to make initial development of the plugin easier and to remove unnecessary complexity at the time.

The downside to this is that the spacing between columns is wonky and buffer names can be unceremoniously cut off when there is space remaining to display them.

The widths should be adjusted dynamically based on the size of the elements and the size of the display (if feasible).

[ryanoneill]

Widths are currently hardcoded via the following functions:

local function icon_width()
  return 5
end

local function buffer_number_width()
  return 5
end

local function buffer_name_width()
  return 40
end