New generation bStat

Version 6 is a complete break from the past, with a greater focus on the activity stream and less support for historical analytics. It is also strictly focused on posts, and has no support for tracking activity on pages that can't be resolved to a post ID.

I added comment tracking ([see `class-bstat-comments.php`](https://github.com/misterbisson/bstat/blob/f4ae247eb8651a4d04e86f7e9bf6e08075c48fc5/components/class-bstat-comments.php)) as an example of how to integrate other plugins so they can track additional activity. Ecommerce events, for example would be nice to integrate. I'm thinking the reporting screen needs to also support actions and filters that allow other plugins to report there as well.

The old tables are abandoned, and this code does not (yet?) have a migrator for any of the data in them. I'm really not sure if any of the old data can be migrated or would have value in the new plugin.

Current condition:
- Reporting is very basic, but better than `print_r()`s. Actually, reporting looks way better thanks to [rickshaw](http://code.shutterstock.com/rickshaw/), [submoduled](https://github.com/misterbisson/bstat/blob/73f715e74d5c95eb4f054d240c3522ce0ccb79c7/.gitmodules).
- Tracking works for me, but needs more testing.
- The tracking JS needs review, and probably performance improvement.
- Click tracking works well enough to appear in the stats, but I fear it's underreporting.