Updating and expanding default_data

[zrush-mitre]

The default_data file included with the TAXII repo is out of date and pretty basic for data to test against. At the very least, this data must be updated to conform with TAXII 2.1 spec. I also recommend adding some to the data to include some complexity, since this is the data that all tests use to ensure accuracy of changes. An extra step would also include a larger set of data, allowing for the speed and efficiency of the server and future changes to be tested.

I have made some changes to the default_data in my PR #62 but is most likely not entirely accurate as well.

[zrush-mitre]

Some work has been done with this since the update to the testing for the server (see #112 and #113), specifically some objects now have multiple versions, and there is an object with two different spec_versions that has opposite version values, so there is a step in the right direction.

I would like to see more work done to expand the data though, especially when backend speed improvements are worked on to include a large amount of data to be parsed to test speeds.