Merge pull request #9 from henrysher/develop

Add utilities for the execution of shell commands
Merge pull request #10 from henrysher/develop

Add the unit tests for the recent utilities
Merge pull request #11 from henrysher/develop

Add a customized interface for local integration test
Merge pull request #12 from henrysher/develop

Bumped to v0.0.3.3
Fix the bug in get_volume_by_instance and add pr-configured options for zones