Begin rewrite for structure analysis script.
Fix logic to 'guess' structure_format based on file name ext.
Changing DUMPData parent class to DUMPReader class.

For consistency with other structure format classes,
DUMPData now sub-classes DUMPReader, and code related to
reading/parsing the dump files moved to the DUMPReader class.
Suspending further development on analyze_structure script.

The analysis code was becoming too customized and tailored to
a specific application, which is inconsistent with the
intent of the scikit-nano scripts. The scripts should provide
a command-line interface for executing the functions and classes
that are utilized in an interactive session, or to run any
GUI apps, which is what the `nanogen` and `nanogenui` scripts
do, respectively.

If I further develop the `StructureAnalyzer` class with general
structure analysis methods, then this script should be developed
further as a CLI to that class.
Removing analyze_structure from docstring directive.
Removing analyze_structure script from setup console_scripts.
Removing _poav_analysis module from sknano.utils.analysis.
Adding code from sknano.utils.analysis._poav_analysis module to
_poav_atom module.
Updating imports for POAV classes. Adding update_attrs method for
backwards compatibility and consistency with parent class method.
updating poav_atoms test module
fix docstring directive
updating setup.py for release of version 0.3.1