Merge pull request #9 from vmware/doc

Guide for installing dependencies
Add custom exceptions.
Remove test_hello.py.
Don't use implicit relative imports.
Merge pull request #10 from vmware/error

Add custom exceptions. Remove test_hello.py.
Add dbee abstract base class.
Merge pull request #11 from vmware/dbee

Add dbee abstract base class.
Add cla.txt.