Perf: speed up 2 methods in railties.

Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

railties/lib/rails/code_statistics.rb

@@ -23,7 +23,7 @@ def to_s
 
   private
     def calculate_statistics
-      @pairs.inject({}) { |stats, pair| stats[pair.first] = calculate_directory_statistics(pair.last); stats }
+      Hash[@pais.map { |pair| [pair.first, calculate_directory_statistics(pair.last)] }]
     end
 
     def calculate_directory_statistics(directory, pattern = /.*\.rb$/)

railties/lib/rails/generators.rb

@@ -140,10 +140,7 @@ def self.find_by_namespace(name, base=nil, context=nil) #:nodoc:
 
       lookup(lookups)
 
-      namespaces = subclasses.inject({}) do |hash, klass|
-        hash[klass.namespace] = klass
-        hash
-      end
+      namespaces = Hash[subclasses.map { |klass| [klass.namespace, klass] }]
 
       lookups.each do |namespace|
         klass = namespaces[namespace]