move tests out from base_test.rb

These tests should be in inheritance_test.rb since its testing a
feature which is implemented in inheritance.rb
fix some typos found in activemodel
SQLite3 3.6.8+ supports nested transactions [ci skip]

http://www.sqlite.org/lang_savepoint.html
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb#L130-L132
refer to the contributing guide on how to create issues.
Merge pull request #9773 from senny/how_to_report_an_issue

refer to the contributing guide on how to create issues.
Merge pull request #9677 from neerajdotname/update-comments-about-kotori

SQLite3 3.6.8+ supports nested transactions [ci skip]
Merge pull request #9765 from tkhr/mv-tests-out-from-base_testrb

Move tests out from base_test.rb to inheritance_test.rb
remove ancient TODOs [ci skip].
Merge pull request #9771 from vipulnsward/fix_typos_activemodel_v1

Fix some typos found in activemodel
Merge pull request #9766 from senny/remove_ancient_todos

Remove ancient TODOs [ci skip]