Save does not have to return false when saving expired item

The previous requirements were too strict. An expired item can still be stored in the cache backend.

Don't sleep() when not required

Merge pull request #42 from php-cache/aequasi-patch-1

Recreating #39

HHVM fix.

Merge pull request #37 from nicolas-grekas/fix

Fix for HHVM

Using \DateTime::createFromFormat('U', time()) instead of new \DateTime('now')

Thank you @nicolas-grekas

Allow for Expire to be not set

Merge pull request #35 from boekkooi/no-expire

Allow for Expire to be not set

Added test to support \Traversable

Thank you @GCDS

Changed return values of isHit after save

Thank you @nicolas-grekas

Updated dependencies

Merge pull request #32 from nicolas-grekas/patch-1

Loosen the composer.json requirements a bit

Test on removal on hierarchy cache

Merge pull request #28 from Nyholm/more_test

Added more test on hierarchy cache

Saving an item with no data should return false and added hierarchy support

Merge pull request #22 from Nyholm/no-data

Test save and fetch item with no data