Use space rate to distinguish minified files.

Minified JS files usually contain less than 2% spaces, while minified
CSS files may contain about 4% spaces. However, an unminified CSS file
may also have as low as 6% spaces, especially when it includes some
resources inline. Consequently, the division might not be appreciate
for CSS files. Even though, it will only mis-recognize a normal file
as minified for a few special cases.

lib/linguist/generated.rb

@@ -72,15 +72,14 @@ module Linguist
 
     # Internal: Is the blob minified files?
     #
-    # Consider a file minified if the average line length is
+    # Consider a file minified if it contains more than 5% spaces.
-    # greater then 100c. Currently only JS and CSS files are
+    # Currently, only JS and CSS files are detected by this method.
-    # detected by this method.
     #
     # Returns true or false.
     def minified_files?
       return unless ['.js', '.css'].include? extname
-      if lines.any?
+      if data && data.length > 200
-        (lines.inject(0) { |n, l| n += l.length } / lines.length) > 100
+        (data.each_char.count{ |c| c <= ' ' } / data.length.to_f) < 0.05
       else
         false
       end