Don't exclude markown md038 warning, close #314

also fix the md038 warning in common/sort.md

pages/common/sort.md

@@ -12,4 +12,4 @@
 
 - Sort passwd file by the 3rd field
 
-`sort -t: -k 3n /etc/passwd `
+`sort -t: -k 3n /etc/passwd`

scripts/markdown-style.rb

@@ -2,4 +2,3 @@
 all
 
 exclude_rule 'MD013'	# Lengthy lines (80+ chars)
-exclude_rule 'MD038'	# Spaces inside code backticks