Add Nord color scheme

Added the "Nord Vim" (1) color scheme. It is also shipped with Nord Vim,
but adding it to lightline itself simplifies the usage for many users.
Mentioned in arcticicestudio/nord-vim#68 (2) by @lokesh-krishna

References:
  (1) https://github.com/arcticicestudio/nord-vim
  (2) https://github.com/arcticicestudio/nord-vim/issues/68

Signed-off-by: Arctic Ice Studio <development@arcticicestudio.com>

autoload/lightline/colorscheme/nord.vim

@@ -0,0 +1,47 @@
+" =============================================================================
+" Filename: autoload/lightline/colorscheme/nord.vim
+" Author: arcticicestudio
+" License: Apache 2.0
+" Last Change: 2017/08/03 09:14:52
+" =============================================================================
+
+let s:nord_vim_version="0.6.0"
+let s:p = {'normal': {}, 'inactive': {}, 'insert': {}, 'replace': {}, 'visual': {}, 'tabline': {}}
+
+let s:nord0 = ["#2E3440", "NONE"]
+let s:nord1 = ["#3B4252", 0]
+let s:nord2 = ["#434C5E", "NONE"]
+let s:nord3 = ["#4C566A", 8]
+let s:nord4 = ["#D8DEE9", "NONE"]
+let s:nord5 = ["#E5E9F0", 7]
+let s:nord6 = ["#ECEFF4", 15]
+let s:nord7 = ["#8FBCBB", 14]
+let s:nord8 = ["#88C0D0", 6]
+let s:nord9 = ["#81A1C1", 4]
+let s:nord10 = ["#5E81AC", 12]
+let s:nord11 = ["#BF616A", 1]
+let s:nord12 = ["#D08770", 11]
+let s:nord13 = ["#EBCB8B", 3]
+let s:nord14 = ["#A3BE8C", 2]
+let s:nord15 = ["#B48EAD", 5]
+
+let s:p.normal.left = [ [ s:nord1, s:nord8 ], [ s:nord5, s:nord1 ] ]
+let s:p.normal.middle = [ [ s:nord5, s:nord3 ] ]
+let s:p.normal.right = [ [ s:nord5, s:nord1 ], [ s:nord5, s:nord1 ] ]
+let s:p.normal.warning = [ [ s:nord1, s:nord13 ] ]
+let s:p.normal.error = [ [ s:nord1, s:nord11 ] ]
+
+let s:p.inactive.left =  [ [ s:nord1, s:nord8 ], [ s:nord5, s:nord1 ] ]
+let s:p.inactive.middle = [ [ s:nord5, s:nord0 ] ]
+let s:p.inactive.right = [ [ s:nord5, s:nord1 ], [ s:nord5, s:nord1 ] ]
+
+let s:p.insert.left = [ [ s:nord1, s:nord6 ], [ s:nord5, s:nord1 ] ]
+let s:p.replace.left = [ [ s:nord1, s:nord13 ], [ s:nord5, s:nord1 ] ]
+let s:p.visual.left = [ [ s:nord1, s:nord7 ], [ s:nord5, s:nord1 ] ]
+
+let s:p.tabline.left = [ [ s:nord5, s:nord3 ] ]
+let s:p.tabline.middle = [ [ s:nord5, s:nord3 ] ]
+let s:p.tabline.right = [ [ s:nord5, s:nord3 ] ]
+let s:p.tabline.tabsel = [ [ s:nord1, s:nord8 ] ]
+
+let g:lightline#colorscheme#nord#palette = lightline#colorscheme#flatten(s:p)

doc/lightline.txt

@@ -229,7 +229,7 @@ OPTIONS						*lightline-option*
 		Currently, wombat, solarized, powerline, jellybeans, Tomorrow,
 		Tomorrow_Night, Tomorrow_Night_Blue, Tomorrow_Night_Eighties,
 		PaperColor, seoul256, landscape, one, Dracula, darcula,
-		Molokai, materia, material, OldHope and 16color are available.
+		Molokai, materia, material, OldHope, Nord and 16color are available.
 		The default value is:
 >
 		let g:lightline.colorscheme = 'default'