Move information on how to contribute to CONTRIBUTORS.rst
Reformat package documentation

Avoid lines larger than 78 characters.
Set package requirements the right way
Update development and CI configurations

* Add suport for code analysis
* Add support for Coveralls
* Test under Plone 4.0/4.1 (Python 2.6) and Plone 4.2/4.3 (Python 2.7)
* Update package classifiers