replaced usage of the deprecated pattern routing key (replaced with path)
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.
use ~2.0 when depending on the CSS selector component

The API is stable and won't change.
use ~2.1 when depending on the ClassLoader component
use ~2.0 when depending on the Dom Crawler component
updated required versions when depending on the Dom Crawler component
updated required versions when depending on the Finder component
updated required versions when depending on the Process component
updated required versions when depending on the Stopwatch component
updated required versions when depending on the Templating component
updated required versions when depending on the Security component
updated required versions when depending on the PropertyAccess component
updated required versions when depending on the OptionsResolver component
updated required versions when depending on the EventDispatcher component
updated required versions when depending on the Routing component
updated required versions when depending on the Translation component
updated required versions when depending on the Validator component
updated required versions when depending on the DependencyInjection component
updated required versions when depending on the Form component