Typo fixes for docs

lib/vagrant/action/builder.rb

@@ -24,7 +24,7 @@ module Vagrant
       end
 
       # Returns the current stack of middlewares. You probably won't
-      # need to use this directly, and its recommended that you don't.
+      # need to use this directly, and it's recommended that you don't.
       #
       # @return [Array]
       def stack

lib/vagrant/action/warden.rb

@@ -7,8 +7,9 @@ module Vagrant
     # exceptional events, and by providing a simple callback, can clean up
     # in any erroneous case.
     #
-    # Except for those who are curious about the internal workings of Vagrant,
-    # Warden will "just work" behind the scenes.
+    # Warden will "just work" behind the scenes, and is not of particular
+    # interest except to those who are curious about the internal workings
+    # of Vagrant.
     class Warden
       attr_accessor :actions, :stack
 

lib/vagrant/provisioners/chef.rb

@@ -1,6 +1,6 @@
 module Vagrant
   module Provisioners
-    # This class is a base class where the common functinality shared between
+    # This class is a base class where the common functionality shared between
     # chef-solo and chef-client provisioning are stored. This is **not an actual
     # provisioner**. Instead, {ChefSolo} or {ChefServer} should be used.
     class Chef < Base

lib/vagrant/util/hash_with_indifferent_access.rb

@@ -1,7 +1,7 @@
 module Vagrant
   module Util
     # A hash with indifferent access. Mostly taken from Thor/Rails (thanks).
-    # Normally I'm not a fan of using an indifferent access hash sine Symbols
+    # Normally I'm not a fan of using an indifferent access hash since Symbols
     # are basically memory leaks in Ruby, but since Vagrant is typically a quick
     # one-off binary run and it doesn't use too many hash keys where this is
     # used, the effect should be minimal.