Fixes https://github.com/rubysherpas/paranoia/issues/274

It looks like ActiveRecord refactored the Transaction class hierarchy in
a non-backwards-compatible
way (https://github.com/rails/rails/pull/16363), which breaks
`add_to_transaction` for null transactions (I think it probably
qualifies as a bug). The workaround is to not try to use
`add_to_transaction` in null transactions.

We're still looking for people to help, but a maintainer now exists

Touching record when restored.

Using guard clauses.

Simplify description in README

I had a hard time comprehending the old wording. I think this is easier to read.

Simplify test setup

* Rely on bundler/setup to setup the load paths

Fixed issue #258: uniqueness validator now works with custom active c…

Introduce #paranoia_destroy_attributes and #paranoia_restore_attributes extension points

Use update_columns rather than touch to update the record, for
generality

Unlike touch, update_columns does not create a transaction for
itself, so we need to add the record to the transaction, if present.
If there is not a current_transaction, the add is a no-op.

This all means that delete will not invoke a transaction or run the
after_commit callbacks unless called from within one, which is
consistent with the Rails docs and the behavior of
ActiveRecord::Base#delete.

Fix uniqueness validator for non-paranoid associations

real_destroy callback

Fix for #122, #121 and #175 on Rails 4 branch

Ruby 1.9's version of `Object.const_get` does not support namespaced constants, so this commit replaces it with `ActiveSupport`'s `#constantize` method.

The tests were failing running JRuby on 1.9 mode. CRuby was not failing because it is not tested against 1.9.

Fixes #114

Fix association class name for namespaced has one model lookups

Use association.klass.name instead of association.class_name to get the
namespaced class name and therefore prevent:

`Object.get_const(association_class_name)`

from raising "uninitialized constant ParanoidHasOne"
in the following situation:

module Something
  def self.table_name_prefix
    "something_"
  end

  class ParanoidHasOne < ActiveRecord::Base
    acts_as_paranoid
    has_one :paranoid_belongs_to, dependent: :destroy
  end

  class ParanoidBelongsTo < ActiveRecord::Base
    acts_as_paranoid
    belongs_to :paranoid_has_one
  end
end

hasOne = Namespaced::ParanoidHasOne.create
hasOne.destroy
hasOne.restore(:recursive => true) # previously would explode

add GoRails video to readme documentation

Fix typo

partial indexes advice