Revert "option column for flagging deletes allowing unique keys to work properly"

This reverts commit 566b1cbd479b061ef41d79b8e345da7351d1d933.

Conflicts:
	README.md
	test/paranoia_test.rb
Add optional sentinel_value

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
Do not restore if attributes are frozen

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