raise error for acts_as_paranoid on models without primary keys

see https://github.com/radar/paranoia/issues/169

Fix usage of paranoia_column in related models

refs https://github.com/radar/paranoia/issues/102

Add compatibility info for rails4

hasOne association could not restore

Conflicts:
	test/paranoia_test.rb

Clear association cache

Fix RSpec 3.x deprecations

Reset paranoia_column before updating it. Fixes #153

This appears to be a Rails ~> 4.0.8 bug, which is seemingly fixed in Rails 4.1.

Use fetch for sentinel_value

Use DateTime for sentinel_value example

Use an epoch. rails convers '0' or 0 to nil for datetime fields

Add test for restore

Update readme

Move MYSQL note to bottom of readme

update destroyed? for sentinel value

This reverts commit 566b1cbd.

Conflicts:
	README.md
	test/paranoia_test.rb

really_destroy! and has_one associations

Fixes #149

Fixes #148

I am tired of supporting Rubinius. I don't use it, nor know of anyone who uses it. Every damn month it breaks on Travis in some new and brilliant way and I don't have the time or energy to support it.

If people truly care about it, then *they* can support it.

The `acts_as_paranoid` gem (v0.4.1) uses assignment followed by a call
to `#save` for restoring a record:

    # in #recover
    run_callbacks :recover do
      recover_dependent_associations(options[:recovery_window], options) if options[:recursive]

      self.paranoid_value = nil
      self.save
    end

This runs any `update` callbacks as well as `recover` callbacks.

Paranoia uses `#update_column` instead of `#save`, so no `update`
callbacks are run when restoring a record.

With this commit the difference in behavior is described in the section
"Acts As Paranoid Migration" of the README.

Fixes #134

Fixes #143

touch_paranoia_column before really_destroy!-ing a record in rails 4.1.x. reloading already really_destroy!-ed associations is needed, otherwise super.destroy! will try to destroy these asociations (because they still exist on the activerecord object, but are already removed from the database)

Fixes #143

FIX: reflections have been reworked in rails 4.1.2 - reflections is no longer available on activerecord objects, only on the class.

Fixes #143

Fixes #143

Update paranoia_test.rb

Fixes #138

Removed deprecated assert_nothing_raised from test.

when the model has_one use class_name or foreign_key, restore use
class_name or setting the foreign_key.