Fix rspec deprecation warnings
Use rspec's `hash_including` if available
Merge pull request #320 from tamird/fix-hash_including

Fix hash_including for rspec 1
Version bump to 1.15.1
Use ancestors' `hash_including` if available.

The previous solution didn't work because rspec does a complicated dance
with module inclusion and inheritence, so we must check this condition
at call-time, rather than include-time.
Merge pull request #323 from tamird/fix-hash_including

Use ancestors' `hash_including` if available.
spec the right thing and fix ruby 1.8
Merge pull request #324 from tamird/fix-hash_including

spec the right thing and fix ruby 1.8