Upgrade to logback 1.1.2

Changelog:
http://logback.qos.ch/news.html
JCLOUDS-410: Remove InputStreamSupplierPayload

ByteSourcePayload replaces this.  jclouds 1.7 deprecated
InputStreamSupplierPayload and Guava 16 deprecated InputSupplier
itself.
JCLOUDS-622: remove calls to InputSupplier methods

Guava 16 deprecated these methods and Guava 18 will remove them.