add I18n support for `:placeholder` HTML option is passed to form fields
[ci skip] updated 'where' in association documention to new style syntax
Fixed AR::Relation#where edge case with Hash and other Relation

Example:

  Author.where(posts: { author_id: Author.where(country_id: 1) }).joins(:posts)
Merge pull request #16438 from agrobbin/input-placeholder-i18n

Add I18n support for `:placeholder` HTML option is passed to form fields
Merge pull request #16502 from bogdan/where-hash-nested-relation

[Regression 4.0 -> 4.1] Fixed AR::Relation#where edge case with Hash and other Relation
Warm up Symbols with where method

Looks like #first wasn't warm enough...
Merge pull request #16501 from tomkadwill/update_delete_to_new_style

[ci skip] updated 'where' in association documention to new style syntax
Use string for order argument, fixed from #16501 [ci skip]
Be sure to reset PK name renamed in the test
extract methods and metaprogram less.
Ignore MySQL "SHOW VARIABLES" when counting queries
Perf optimization for `url_for` called w/ Hash

Benchmarking the existing code:

```ruby
{ :only_path => options[:host].nil? }.merge!(options.symbolize_keys)) 
```

Against optimized code, that does not require a new hash or a merge:

```ruby
options = options.symbolize_keys
options[:only_path] = options[:host].nil? unless options.key?(:only_path)
options
```

We see a statistically significant performance gain:

![](https://www.dropbox.com/s/onocpc0zfw4kjxl/Screenshot%202014-08-14%2012.45.30.png?dl=1)

Updated to not mutate incoming parameters
Merge pull request #16504 from schneems/schneems/fix_url_for

Perf optimization for `url_for` called w/ Hash
Spelling errors
Merge pull request #16508 from jbsmith86/master

Spelling errors
s/Dont'/Don't/
create_table + transactional_fixtures = :bomb:
Use the method for determining attribute methods rather than duplicating

I've been trying to reduce the number of places that care about
`attributes`, and its existence. We have a method for this check, let's
use it instead.
Merge pull request #16505 from sgrif/sg-attribute-internals

Use the method for determining attribute methods rather than duplicating
prefer `has_attribute?` over `attributes.key?`.

Follow up to the discussion on #16505.