Hi Dominik,
I've some problems with last version of the library. This is the error.
WEB-INF/lib/facelets-taglib-jsf12-spring-3-0.5.jar!/META-INF/faces-config.xml: Error at line 7 column 23: cvc-elt.1: Cannot find the declaration of element 'faces-config'.
at com.sun.faces.config.ConfigureListener.parse(ConfigureListener.java:1438)
at com.sun.faces.config.ConfigureListener.contextInitialized(ConfigureListener.java:348)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3972)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4467)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:546)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:637)
The workarround for me is edit the faces-config.xml that is inside the jar and remove several lines that are commented. The error does not occur all the time, it seems that occur only when there is no Internet connection.