Merge branch 'amnesia-0.2.x' into amnesia-3

Conflicts:
	CHANGELOG.md
	Gemfile.lock
	ext/mysql2/client.c
	ext/mysql2/extconf.rb
	lib/mysql2.rb
	lib/mysql2/version.rb
	spec/mysql2/client_spec.rb
	spec/mysql2/error_spec.rb
Removed files from 3.x