Fixes fetch documentation in package docstring.

This corrects several lines that relate to the changes to fetch brought
in by Pull Request #156.
Merge pull request #157 from gotgenes/bugfix-update_fetch_documentation

Fixes fetch documentation in package docstring.
Removes setup import from distutils that overrides setuptools setup.
Tidies up Python 2.6 dependencies

Moves all dependencies to the install_requires argument to setup.
Updates PyPI trove classifiers.
Use requirements files to consolidate dependencies.