add MULTI, DISCARD and EXEC functions
Merge pull request #15 from M6Web/add-multi-and-exec-functions

Add MULTI, DISCARD and EXEC functions
Merge branch 'master' of github.com:M6Web/RedisMock into feature/ttl
Full tests of expire/ttl
Remove extra line
small corrections
Merge pull request #13 from M6Web/feature/ttl

ttl & expire
Merge branch 'master' of github.com:M6Web/RedisMock into feature/hdel

Conflicts:
	tests/units/RedisMock.php
Add expire tests for hdel