This introduces a significant breaking change, and I don't expect it to
be merged off-hand. I do think that it's worth discussion, since it
seems like a very idiomatic choice in terms of how errors would be handled.

A similar backwards-incompatible change was introduced in e6e6411,
allowing the app's Run method to return an error.

This is a way to provide hidden flags for app, command and subcommands

For example:

  --generate-bash-completion global flag shouldn't be printed along
  with other flags as it might generally confuse people into thinking
  that 'generate' in-fact would generate a bash completion file for them
  to be used along with their app.

Also in general one would want to hide some flags for their apps.

to ensure the intent, responsibility, and migration path are all more clear.

Merging #201 - @harshavardhana's hidden flags impl (and more!)

Cleaning up the recently-introduced deprecations

Add some explicit docs about help text customization

…rinyx-action-err

Merging #135 😻

	Exit code example produces now correctly,
	https://github.com/codegangsta/cli#exit-code

	```
	$ ./ec --ginger-crouton=false
	it is not in the soup
	$ echo $?
	86
	$
	```

…) was missing

Closes #376

Ensure HandleAction/HandleExitCoder work correctly with *ExitError

 into PaulMakepeace-fix-err-assertion

Version 1.16.0 prep