Exception handling for controllers using ActionController::Live

Any exceptions that occured at the view or controller level for a
controller using ActionController::Live would cause the server to either
hang with an open socket indefinitely, or immediately crash (depending
on whether the server was launched with rails s or directly). Changed
the behavior of exceptions to act the same as streaming templates for
html requests, and allow for an on_error callback if needed.
rails commands even if bin/rails is a gem stub
failure to parse params should trigger a 400 Bad Request
Remove “Sweepers” from Caching TOC and mention Page/Action caching are removed
script/rails could never be from bundler
need to delete bin, not binstub, update wording
Improve poor security recommendation in docs

As reported in #9960, the current documentation recommends an insecure practice for
key generation from a password (a single round of SHA-256). The modified documentation
uses ActiveSupport::KeyGenerator to perform proper key stretching.
Revert "Using American English spellings over British style spellings"

This reverts commit 573df1cf2a5d5d1f288c8a4a5d76194675141832.

Reason: changelog edits aren't allowed in docrails.

[ci skip]
Merge branch 'master' of github.com:rails/rails
minor copy editing
fix binstub typo
Fix typo
Remove unnecessary / confusing code in example
as of Rails 3.2.13 it appears that importing an engine's migration into the host app is achieved by rake blorgh_engine:install:migrations
fixed a article link at sitepoint
Merge pull request #132 from hlee/master

Fixed an article link at sitepoint
Merge pull request #129 from rafBM/master

Remove “Sweepers” from Caching TOC and mention Page/Action caching removal
Proofreading tweaks to the Mailer guide
Merge pull request #131 from lazylester/master

Edge rails new syntax for importing engine migration
Escape multibyte line terminators in JSON encoding

Currently, json/encoding respects the JSON spec (as it should) which 
disallows \n and \r inside strings, escaping them as expected.

Unfortunately, ECMA-262 (Javascript) disallows not only \n and \r in 
strings, but "Line Terminators" which includes U+2028 and U+2029. 
See here: http://bclary.com/2004/11/07/#a-7.3

This pull request adds U+2028 and U+2029 to be escaped.

# Why? 

It's very common to see something like this in a Rails template:

<script type="text/javascript"> 
var posts = <%= @posts.to_json %>;
</script>

If U+2028 or U+2029 are part of any attributes output in the to_json
call, you will end up with an exception.
In Chrome: Uncaught SyntaxError: Unexpected token ILLEGAL 

# Why not?

This is JSON encoding, and the JSON spec is specific about how to 
encode strings. U+2028 and U+2029 don't get special treatment.

Just trying to start a discussion... what do you do in your apps
to deal with this? Is there a convention I'm missing?