Update README.md
Updated to reference new COBRApy v0.3.0b1
Fixes bugs, and pytest settings.

- Moved to absolute imports (please use virtualenv)
- Fixed bug with merging nodes
Merge branch 'master' into ipython-fixes

Conflicts:
	escher.1.0.dev.min.js
	escher/plots.py
	escher/tests/test_urls.py