Gather statistics about made predictions

[dnesteryuk]

The client will send information about made predictions. The engine should store that info and there should be a simple command which can be called from the command-line in order to see info about correct predictions VS incorrect ones.

The idea of this task is to track how the model works for a particular site.

[dnesteryuk]

The scope of this task is big for the initial (0.0.1) release. It isn't hard to store data, but the written metrics should be well displayed in some chart. Therefore, this task should wait for an admin interface which will be accessed through the web.