Only do pickles report on feature files within the project

Update to 0.2.0 went smoothly - but I found that pickles is picking up feature files that aren't ready/aren't in my testing project, which caused the reporting to fail.

Essentially, the team uses my "Features" project to draft out feature files as well. Until they are actually added to the csproj, I'm unsure of the quality.

While this could be rooted as an issue of my project team's workflow, I think if the csproj is used as a metric this could be something to lock down.

If that's not feasible, I think adding tag filter support would work as well.

Using FeatureLint before a project build is also an option, as it is costly to resources to run all the acceptance tests only to have it fail on the Pickles report.