Remove Ruby <1.9 core extensions

lib/jekyll/core_ext.rb

@@ -54,14 +54,6 @@ class Hash
   end
 end
 
-# Thanks, ActiveSupport!
-class Date
-  # Converts datetime to an appropriate format for use in XML
-  def xmlschema
-    strftime("%Y-%m-%dT%H:%M:%S%Z")
-  end if RUBY_VERSION < '1.9'
-end
-
 module Enumerable
   # Returns true if path matches against any glob pattern.
   # Look for more detail about glob pattern in method File::fnmatch.
@@ -74,13 +66,7 @@ end
 # read_with_options ignore optional parameter for 1.8,
 # and act as alias for 1.9 or later.
 class File
-  if RUBY_VERSION < '1.9'
-    def self.read_with_options(path, opts = {})
-      self.read(path)
-    end
-  else
-    def self.read_with_options(path, opts = {})
-      self.read(path, opts)
-    end
+  def self.read_with_options(path, opts = {})
+    self.read(path, opts)
   end
 end