Fix minor bug

Fix a typo in report (parser instead of parse)
Plus force default value/return.
Fix PEP8.
[tests] Add new skipfish reports.
[ptp] Homogenize PEP8.
[report] Fix typo.
[parser] Skeleton of the parser abstract class.
[arachni] Add parser for 0.4.6 XML report.
[skipfish] Add parser for 2.10b JSON report.
[w3af] Add parser for 1.6.0.2 XML report.
[wapiti] Add parser for 2.3.0 XML report.
[report] Support new parsing architecture.
[tools] Support new parsing architecture.
[info] Simply use a dict instead of the Info class.

I think that the Info class adds nothing to a standard dictionnary.
Therefore I updated PTP in order to use a simple dictionnary instead of a
custom class.
[report] Use iterator when looping over dict's keys.
[report] Remove unnecessary try/catch in `is_mine`

Parsers' `is_mine` method does not throw NotSupportedVersionError.
[doc] Configuration doc for sphinx.
[doc] Small sphinx docstrings for trying.
[doc] Doc of ptp and libptp basic classes.

Still have to document the specialized Report and Parser classes.
[doc] Fix typo in AbstractParser docstring.
[test] Enhance test suite.