Simple patch to allow at least some functionality with Chef Solo

Chef::DataBag.list triggers an error when used with Chef Solo (not sure what's the exact cause of the symptom) so a simple check allow using the non-data_bag parts with Chef Solo.
travis: pin chefspec to 1.3 for ruby 1.8
travis: test also with ruby 2.0 and chef 11
Merge remote-tracking branch 'upstream/master' into patch-1
Fix tests and simplify chef-solo support patch

Since data_bag "<name>" silently returns an empty list of data_bag_items if the
data_bag does not exist, the whole process works even in the simplified version
without the Chef::DataBag.list check that isn't supported on chef-solo.
Fix 1.8.7 "compatibility"
Merge pull request #1 from cmur2/patch-1

Simple patch to fix data bag handling for chef solo