Add sanitise.py, a script that does sanitisation and archival

This implements: https://trac.torproject.org/projects/tor/ticket/13563
Additionally add example data.
Change sanitised yaml output format to include explicit start and end
Update example sanitised output
Set default_flow_style to False in order to get produce correct sanitised format
Update example of sanitised file
Close the report file before deleting it and make file removal clearer
Merge pull request #1 from olliwolli/master

Add sanitise.py, a script that does sanitisation and archival