use send() for #attribute_was (private in Rails 4.0)

[jeanmartin]

private method 'attribute_was' called for ... is what you currently get trying to use paper_trail (6.0.2) with Rails 4.0(.13). See similar problem in lwe/simple_enum#70.

[jaredbeck]

Hi Jan, This looks good, but please add:

1. a comment like TODO: after dropping support for rails 4.0, remove send, because attribute_was is no longer private.
2. a changelog entry under "fixed"

Also, please upgrade your copy of rails as soon as possible. Rails 4.0 has reached EOL. We have already stopped testing against rails < 4.2, and will probably change our gemspec soon to forbid rails < 4.2.

[jaredbeck]

Jan, Here's a friendly reminder to please make the requested changes. Thanks!

[goodviber]

Hi, is the change implemented?

[jaredbeck]

Hi, is the change implemented?

No, this PR requires changes by Jan and will be closed soon if they are not made.

[jaredbeck]

Closing via #936, which also resumes CI testing against AR 4.0 for now, but please please please upgrade your EOL rails ASAP.

Thanks for bringing this to our attention, Jan.