Ignore warning about using `this`

We currently get a `golint` warning when using the `this` keyword.  I personally like it as does @jamlen who implemented so.... I propose we add the following error output to the grep of what we ignore from the ruleset.

```
core/SummaryBuilder.go|58 col 1 warning| receiver name should be a reflection of its identity; don't use generic names such as "this" or "self"
```