Removed useless commons-lang dependency.
Backported tests from AssetLocator.
Fixed broken test. WebJarAssetLocator was not correctly behaving when folderPath didn't start with /.
Remove reflections API usage.

First all JARs/folders of the classpath defining a META-INF/resources/webjars are identified. Then all contained files are examined based on the provided pattern. Both directories and JARs are supported.