UPGRADE FROM 2.x to 3.0

ClassLoader

The UniversalClassLoader class has been removed in favor of ClassLoader. The only difference is that some method names are different:
- registerNamespaces() -> addPrefixes()
- registerPrefixes() -> addPrefixes()
- registerNamespaces() -> addPrefix()
- registerPrefixes() -> addPrefix()
- getNamespaces() -> getPrefixes()
- getNamespaceFallbacks() -> getFallbackDirs()
- getPrefixFallbacks() -> getFallbackDirs()
The DebugUniversalClassLoader class has been removed in favor of DebugClassLoader. The difference is that the constructor now takes a loader to wrap.

HttpKernel

The Symfony\Component\HttpKernel\Log\LoggerInterface has been removed in favor of Psr\Log\LoggerInterface. The only difference is that some method names are different:
- emerg() -> emergency()
- crit() -> critical()
- err() -> error()
- warn() -> warning()
The previous method renames also happened to the following classes:
- Symfony\Bridge\Monolog\Logger
- Symfony\Component\HttpKernel\Log\NullLogger
The Symfony\Component\HttpKernel\Kernel::init() method has been removed.
The following classes have been renamed as they have been moved to the Debug component:
- Symfony\Component\HttpKernel\Debug\ErrorHandler -> Symfony\Component\Debug\ErrorHandler
- Symfony\Component\HttpKernel\Debug\ExceptionHandler -> Symfony\Component\Debug\ExceptionHandler
- Symfony\Component\HttpKernel\Exception\FatalErrorException -> Symfony\Component\Debug\Exception\FatalErrorException
- Symfony\Component\HttpKernel\Exception\FlattenException -> Symfony\Component\Debug\Exception\FlattenException

Routing

Some route settings have been renamed:

The pattern setting for a route has been deprecated in favor of path
The _scheme and _method requirements have been moved to the schemes and methods settings

Before:

article_edit:
    pattern: /article/{id}
    requirements: { '_method': 'POST|PUT', '_scheme': 'https', 'id': '\d+' }

<route id="article_edit" pattern="/article/{id}">
    <requirement key="_method">POST|PUT</requirement>
    <requirement key="_scheme">https</requirement>
    <requirement key="id">\d+</requirement>
</route>

$route = new Route();
$route->setPattern('/article/{id}');
$route->setRequirement('_method', 'POST|PUT');
$route->setRequirement('_scheme', 'https');

After:

article_edit:
    path: /article/{id}
    methods: [POST, PUT]
    schemes: https
    requirements: { 'id': '\d+' }

<route id="article_edit" path="/article/{id}" methods="POST PUT" schemes="https">
    <requirement key="id">\d+</requirement>
</route>

$route = new Route();
$route->setPath('/article/{id}');
$route->setMethods(array('POST', 'PUT'));
$route->setSchemes('https');

Translator

The Translator::setFallbackLocale() method has been removed in favor of Translator::setFallbackLocales().

Twig Bridge

The render tag is deprecated in favor of the render function.

Yaml

The ability to pass file names to Yaml::parse() has been removed.

Before:
```
Yaml::parse($fileName);
```
After:
```
Yaml::parse(file_get_contents($fileName));
```