init: use nlinum instead of linum

nlinum from Elpa seems to handle the line number margin differently
from linum. This avoids a horizontal gap between left margin and fringe
when line numbers are downscaled with respect to the text font size.

See:
  https://emacs.stackexchange.com/questions/53598/\
    how-to-downscale-linum-font-size-and-avoid-left-margin-gap
diff --git a/init/init.el b/init/init.el
index e33b1c4..42266b1 100644
--- a/init/init.el
+++ b/init/init.el
@@ -38,10 +38,8 @@
 
 (add-to-list 'package-archives
 	     '("melpa" . "https://melpa.org/packages/") t)
-;; If running below the recommended Stretch version
-(when (< emacs-major-version 24)
-  (add-to-list 'package-archives
-	       '("gnu" . "https://elpa.gnu.org/packages/")))
+(add-to-list 'package-archives
+	     '("gnu" . "https://elpa.gnu.org/packages/"));)
 
 (package-initialize)
 
@@ -51,7 +49,8 @@
 	smooth-scroll
 	markdown-mode
 	smart-mode-line-powerline-theme
-	rainbow-delimiters))
+	rainbow-delimiters
+	nlinum))
 
 (unless package-archive-contents
   (package-refresh-contents))
@@ -73,8 +72,9 @@
     ("84d2f9eeb3f82d619ca4bfffe5f157282f4779732f48a5ac1484d94d5ff5b279" default)))
  '(fill-column 80)
  '(global-hl-line-mode t)
- '(global-linum-mode t)
- '(inhibit-startup-screen t)
+ '(nlinum-highlight-current-line t)
+ '(global-nlinum-mode t)
+  '(inhibit-startup-screen t)
  '(show-paren-mode t)
  '(tool-bar-mode nil))
 
@@ -83,12 +83,13 @@
 ;;'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''';;
 (custom-set-faces
  '(default ((t (:background "#343D46" :foreground "#D8DEE9" :slant normal
-			    :weight normal :width ultracondensed
-			    :foundry "adobe" :family "Source Code Variable"))))
+			    :weight normal :width normal :foundry "adobe"
+			    :family "Source Code Variable"))))
  '(font-lock-comment-face ((t (:background "#343D46" :foreground "#848B97"))))
  '(fringe ((t (:background "#343D46"))))
- '(hl-line ((t (:background "#2C3133"))))
- '(linum ((t (:slant normal :width ultracondensed :foreground "#848B97"))))
+ '(hl-line ((t (:background "#2C3133" :weight bold))))
+ '(nlinum-current-line ((t (:background "#2C3133" :foreground "white" :weight bold :height 80))))
+ '(nlinum ((t (:slant normal :width ultra-condensed :foreground "#848B97"))))
  '(mode-line ((t (:background "#4E5A65" :foreground "#D8DEE9" :box nil))))
  '(mode-line-buffer-id-inactive ((t (:inherit mode-line-buffer-id
 					      :background "#757B81"
@@ -175,12 +176,12 @@
 ;;,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,;;
 ;; Fringe
 ;;'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''';;
-(fringe-mode '(12 . 0))
+(fringe-mode '(10 . 0))
 
 ;;,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,;;
 ;; Line number format
 ;;'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''';;
-(setq linum-format "%5.5s")
+(setq nlinum-format "%5.5s")
 
 ;;,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,;;
 ;; Highlight matching bracket
@@ -245,8 +246,8 @@
 ;;,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,;;
 ;; Furter customization for linum and left margin width
 ;;'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''';;
-;(eval-after-load "linum"
-;  '(set-face-attribute 'linum nil :height 80))
+(eval-after-load "nlinum"
+  '(set-face-attribute 'linum nil :height 80))
 (set-default-font "Source Code Variable-12")
 
 ;;,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,;;