corobo Usage Stats

From @prnvdixit:
> Identify the most regularly used corobo commands.
> This task involves three parts:
>
> - Designing the database to store (command, frequency) pairs
> - Updating the table on each command (or buffer commands, if you're worried about performance)
> - An interface to view the results
>
> Contributors most likely to help regarding issue : @meetmangukiya
>
> label : initiatives/gci

Migrated from https://github.com/coala/coala/issues/4784

The issue does not name files, tests, or an entry point. Start by locating where corobo commands are handled and how persistent data and user-facing interfaces are organized. Done means usage pairs are stored, updated per command or in a defined buffer, and viewable through an interface.

Written by the indexing model from the issue text.