add zmq network connection

New network module added. The BaseConnection allows support for multiple
network connections.

	new file:   yerba/network.py
Move module yerba to fix name conflicts

The yerba module now doesn't collide with the package name. Updated
yerba package to export Yerba class. Fixed yerbad script to use new
export.

	modified:   bin/yerbad
	modified:   yerba/__init__.py
	renamed:    yerba/yerba.py -> yerba/base.py
use ZMQConnection in base module

Removed network code from base module and refactored the code to use
network module ZMQConnection. Remove duplicate RequestError from base.

	modified:   yerba/base.py
add log helper function

Refactor yerbad script to now use a get_logger helper function in the
yerba package.

	modified:   bin/yerbad
	modified:   yerba/__init__.py
rename use of id to workflow_id

A variable should not redefine a built-in function.

	modified:   yerba/managers.py
Fix syntax error

	modified:   yerba/managers.py
update Status type in core

Remove Terminated and Waiting from Status. Add Stopped and Initialized
to Status.
add setup.py to project

	modified:   setup.py