correct spelling errors and typos in documentation.
add warning about silex migration.
Fix typo in `scarlarToString` method name.

This is a protected function and is not called anywhere else but this class, so this is safe to rename.
Merge pull request #13 from bangpound/patch-1

Fix typo in `scarlarToString` method name.
Merge pull request #12 from bangpound/docs

Improve documentation
Normalize YamlFileLoader accordingly to JsonFileLoader
Merge pull request #14 from bastnic/patch-1

Normalize YamlFileLoader accordingly to JsonFileLoader
Update CHANGELOG.md