Support Rails 4

Hey there. I've been updating axlsx_rails to support Rails 4.1, and found you need this change for acts_as_axlsx. The find(:all) method is no longer available.

I don't see any explicit documentation for passing options to the find(:all) method. I've guessed for Rails 4.1 that where(conditions) and order(order) would be useful. Perhaps the data option should be documented. Thoughts?