updated required versions when depending on the Yaml component

The API has not changed since 2.0 and won't until 3.0.
use ~2.0 when depending on the locale component

Some methods have been added in 2.1 but none of them are used by the
Symfony components.
updated required versions when depending on the Translation component
updated required versions when depending on the Config component
updated required versions when depending on the HttpFoundation component