Merge pull request #3 from aluuu/master

Add PTTL/PEXPIRE commands and tests on common commands
Merge pull request #4 from aluuu/master

Some commands, more tests and Travis CI script
fix RANDOMKEY test
Add TYPE command test case
Add INCRBYFLOAT command
Fix some style issues
Add APPEND command test case
Add INCR*/DECR* commands test case