RBTools commands were previously using print and sys.stderr 

to output messages. This change abstracting outputting by using a 

wrapper around a stream output object. This makes it easier to customize 

output streams and suppress output. 4 wrappers (2 for standard output 

unicode and byte, 2 for standard error unicode and byte) are initiated 

in the Command class that is accessible to all child classes.

Ran all tests in ./tests/runtests.py rbtools.commands and passed.
Added two new tests for __init__.py. One that tests if output stream 

object is set correctly for OutputWrapper and another test that makes 

sure OutputWrapper passes the correct message to the output stream object