Better docs, conda based install.

- Enable numpydoc extension
- Use ReadTheDocs theme,
- Add docs sections: Install and devel
- Conda based build (bug fixed conda-build 1.9 upstream )
- better setup.py
- Rel. import in __init__.py
- Make travis build inplace (py.test tests local tree)
- Use python library from conda environment for distutils based local build.
- Fix Py3 issue: reduce -> functools.reduce
- Update .travis.yml