Upgrade to Guava 14.0

Release notes:
https://code.google.com/p/guava-libraries/wiki/Release14
Merge pull request #1369 from shrinandj/fix_s3_directory_suffix

Make AWS-S3 use the right directory suffix.
Merge pull request #1370 from maginatics/guava-14.0

Upgrade to Guava 14.0
Merge branch 'master' of https://github.com/shrinandj/jclouds