Stop testing on 1.8.7, 1.9.2, rbx-18mode, and rbx-19mode.
Adding Rails 4 and its dependent gems.

Unfortunately we can't just use only activerecord, since it's not released as stand alone gem.

Also:
* Replacing all .scoped calls with .all
* Using new order syntax on AR associations
* Replaced deprecated finder methods
* Using to_a for comparing activerecord relations in specs.
* Using correct activerecord syntax in nested_set_scope method
Use only activerecord, not all of Rails.
attr_accessible was removed from activerecord.
Let specs run and fix deprecation warnings about default_scope.
Delegate connection to class

Rails 4 has deprecated the instance connection method, this adds a delegation method back to skip the deprecation warning
Merge pull request #184 from lexrupy/rails4

Delegate connection to class
Merge branch 'master' into rails4

Conflicts:
	.travis.yml
	lib/awesome_nested_set/awesome_nested_set.rb
	spec/awesome_nested_set_spec.rb
Merge branch 'master' into rails4

Conflicts:
	lib/awesome_nested_set/awesome_nested_set.rb
Fix specs and deprecation warnings.
Use jdbc adapters that are compatible with AR 4.0
Merge remote-tracking branch 'ugisozols/fix_specs' into rails4
fixed README.rdoc => README.md

Closes #198
Merge branch 'rails4'

Conflicts:
	awesome_nested_set.gemspec