Adds remembering of the locale before an asynchronous task is run.
Sets the remembered locale when an asynchronous task is run.
Merge branch 'master' into fix-locale-not-recognized

Conflicts:
	lib/devise/async/backend/base.rb
	test/devise/async/backend/base_test.rb
Merge pull request #1 from baschtl/fix-locale-not-recognized

Fix locale not recognized when sending mails asynchronously