fix code style (.zero? instead of == 0)

Author: toy

lib/image_optim/space.rb

@@ -15,7 +15,7 @@ def self.space(size)
       else
         log_denominator = Math.log(size.abs) / Math.log(BASE)
         degree = [log_denominator.floor, SIZE_SYMBOLS.length - 1].min
-        number_string = if degree == 0
+        number_string = if degree.zero?
           size.to_s
         else
           denominator = BASE**degree

spec/spec_helper.rb

@@ -78,12 +78,12 @@ module CapabilityCheckHelpers
   def any_file_modes_allowed?
     Tempfile.open 'posix' do |f|
       File.chmod(0, f.path)
-      File.stat(f.path).mode & 0o777 == 0
+      (File.stat(f.path).mode & 0o777).zero?
     end
   end
 
   def inodes_supported?
-    File.stat(__FILE__).ino != 0
+    !File.stat(__FILE__).ino.zero?
   end
 
   def signals_supported?