deep_munge solves CVE-2013-0155 security vulnerability, but its
behaviour is definately confuisng. This commit adds logging to deep_munge.
It logs keys for which values were set to nil.

Also mentions in guides were added.

Also make all three examples consistent.

[ci skip]

This is a follow up to #12609 and integrates #12158.

Thanks @aspiers.
Closes #12158.

Code style adherence

Add .try to prevent undefined method error for NilClass.

The previous example of how to permit a hash of unknown keys used .tap, but had the side effect of logging an "Unpermitted parameters" message despite being a successful workaround. The proposed workaround is ever so slightly better, imo, because it won't result in an "Unpermitted parameters" message being logged.

* Indent after private/protected
* Ruby >= 1.9 syntax for hashes
* Prefer method { do_stuff } instead of method{do_stuff} for single-line blocks.

[ci skip]

I'm adding documentation to the action_controller_overview guide which
should tell people how to stream arbitrary data.

http://stackoverflow.com/questions/8501021/rails-json-request-is-not-parsed-correctly-into-post-parameters

- Consistent hash structure
- Rewording / typo fixes

The error that's raised in case the required key is missing it's actually `ActionController::ParameterMissing` not `ActionController::MissingParameter`. It's important to fix so that people reading the guides knows what error to rescue from when needed.

This replicates the situation described in
https://github.com/rails/strong_parameters/issues/114

Closes #9558.

Origin: #9534.

The current ActionController guide does not mention strong parameters
at all. I integrated the README into the guide to explain the API.

I also included a section to illustrate that the API does not solve
all possible whitelisting scenarios.

The origin was #9454.

If you want an ability to parse XML parameters, please install
`actionpack-xml_parser` gem.

Introduce ./bin for your app's executables: bin/bundle, bin/rails, bin/rake. Executable scripts are versioned code like the rest of your app. To generate a stub for a bundled gem: 'bundle binstubs unicorn' and 'git add bin/unicorn'