install phpunit & latest zend framework in composer
added php 5.5 to travis settings and install composer packages with --prefer-source to avoid timeouts
avoid using arrays with array_unique() as arrays are converted into strings
1 second lifetime difference is acceptable for the cache touch test
Merge pull request #89 from aporat/master

composer and phpunit changes
check new return value (-2 if the key does not exist)
error prefix in exception message
new stable version
error reply with different prefixes
changed redis ports
changed ports in tests config
STABLE_REDIS_VERSION = '2.8.0'
updated changelog
Merge pull request #91 from DmitryGeometria/redis2.8

Redis 2.8 support
Merge remote-tracking branch 'upstream/master'