Upgrade to Guava 16.0.1

Guava < 16.0.1 has issues with jdk 1.7.0_51-b51. See https://code.google.com/p/guava-libraries/issues/detail?id=1635 

People should really not run older Guava versions on the new jdk and httpcache4j uses previously deprecated Guava methods which have been removed from Guava 16, making it impossible to use httpcache4j and Guava 16.

This pull request upgrades httpcache4j to Guava 16.0.1 and removes usage of deprecated classes/methods in Guava.