activerecord/examples/simple.rb use master branch activesupport gem

### Before
-----------

```ruby
ruby activerecord/examples/simple.rb

home/tumayun/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in `require': cannot load such file -- active_support (LoadError)
	from /home/tumayun/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in `require'
	from /home/tumayun/workspace/gems/rails/activerecord/lib/active_record.rb:24:in `<top (required)>'
	from /home/tumayun/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in `require'
	from /home/tumayun/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in `require'
	from activerecord/examples/simple.rb:2:in `<main>'
```

### After
------------

```ruby
ruby activerecord/examples/simple.rb

#<ActiveRecord::Relation [#<Person id: 1, name: "bob">]>
#<ActiveRecord::Relation []>
```