Print filename before executing policy

Closes #156 (closed)

Output looks like this:

*********************************************************
Executing policies from policies/missing-description.yml.
*********************************************************
Performing a dry run.

============================
Triaging the `REDACTED` group
============================

---------------------------
Processing rules for issues
---------------------------

---------------------------------------------------
Processing rule: **Issue is missing a description**
---------------------------------------------------
.

* Found 43 resources...
* Filtering resources...
* Total after filtering: 0 resources
* Limiting resources...
* Total after limiting: 0 resources

The following comments would be posted for the rule **Issue is missing a description**:

...