added String#to_date documentation to Rails 4 upgrade guide

[ci skip]
Generate namespaced routes correctly for generators. Fix for #11532
Merge pull request #11756 from zilkey/master

added String#to_date documentation to Rails 4 upgrade guide [ci skip]
test-case for fixed issue #11870.
Merge pull request #11544 from prathamesh-sonpatki/namespaced_routes_test

Generate namespaced routes correctly for generators. Fix for #11532