Use Pathname v0.4.0

Since the return values of some methods have changed, we use gem to fix the behavior.

Author: ksss

Gemfile

@@ -29,6 +29,7 @@ group :libs do
   gem "dbm"
   gem "mutex_m"
   gem "nkf"
+  gem "pathname"
 end
 
 group :profilers do

Gemfile.lock

@@ -71,6 +71,7 @@ GEM
     parser (3.3.7.0)
       ast (~> 2.4.1)
       racc
+    pathname (0.4.0)
     power_assert (2.0.5)
     pstore (0.1.4)
     psych (4.0.6)
@@ -177,6 +178,7 @@ DEPENDENCIES
   net-smtp
   nkf
   ostruct
+  pathname
   pstore
   raap
   rake