Increase test coverage of iteration operations

[cheesema]

Would be great to include some test coverage on:

• The random access components of the GenIterator.
• The access components of the APRTree.
• Find particle cell from spatial point.
• Reconstruction Condition test.
• Compression Class.

[MSusik]

BTW, if you want the repo to be very fancy, you can automatically measure test coverage:

https://github.com/codecov/example-cpp11-cmake

I can help you with setup if needed.

[cheesema]

This sounds both cool and daunting. Scared once we get back a number :). But definitely is something we should look at. I'll let you know.

[cheesema]

@joeljonsson I think this would now be a good move. Some help setting it up would be great if you have the time (@MSusik) ?

[MSusik]

I'm very busy in recent days, but once I find some time, I can take care of that.