Removed validation for col#width

This needs to be smarter and only validate when the user supplies a
value directly. 10% performance increase just by removing the
validataion as this gets updated every time we set a single cell value.

lib/axlsx/workbook/worksheet/col.rb

@@ -104,7 +104,12 @@ def style=(v)
 
  # @see Col#width
  def width=(v)
- Axlsx.validate_unsigned_numeric(v) unless v == nil
+ # Removing this validation make a 10% difference in performance
+ # as it is called EVERY TIME A CELL IS ADDED - the proper solution
+ # is to only set this if a calculated value is greated than the
+ # current @width value.
+ # TODO!!!
+ #Axlsx.validate_unsigned_numeric(v) unless v == nil
  @custom_width = @best_fit = v != nil
  @width = v
  end