Fixes for AA 0.6.1

[alepore]

With AA 0.6.1 i get
undefined local variable or method max_csv_records' for #Admin::MyModelController:0x007fe69b29a278`

This is because the method was removed in this commit activeadmin/activeadmin@a8ad4f9
Using max_per_page should be the same, right?

Tests was green just because AA 0.6.0 was forced by Gemfile.lock.
I think it's a good practice do not include it in gems, read here: http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile

[thimios]

bumped on the same issue using AA 0.6.2 would be great to merge this pull request