Add eCommerce support

This PR does a few things:

* Adds eCommerce support (Fixes #17).  Specifically for WooCommerce and WP eCommerce.
* Prefixes filter names, functions names (and much else) with Segment, rather than Segment_IO
* Adds a fully baked page() method.
* Adds a class to help with client-side handling of server-side events.
* Features Bob Ross quotes in commit messages.
we should call `$page` `$name` instead i think?

and we should add the `$category` support like analytics.js has, so that you can pass an optional category as the first argument