Issue 423 - Add coverage data to compare view

[rishijain]

Check list:

• Add an entry to the changelog
• Squash all commits into a single one
• Describe your PR, link issues, etc.

This fixes issue: #423
I noticed that we are not passing any coverage data and the default value of it being 0, it shows 0% against all the files for compare build view.

[santhosh-fit]

@nunosilva800 could you review and merge this please? I am starting to use rubycritic and showing the correct coverage info on build/compare would be helpful.

[etagwerker]

@rishijain How does this work? I don't understand what's the goal of this PR.

I think it's a tricky problem to solve: To show the difference in coverage between two branches.

The main issue is this: People don't usually check in their coverage directory (so the coverage artifacts are going to be the same across two branches) which makes it very tricky to show a comparison of coverage data.

In order to show a useful comparison in coverage data, then we would have to rely on the user running the test suite in one branch, storing the coverage resultset artifact, then another, then store the new artifact, then run rubycritic and then compare this.

I'm inclined to not support this in the compare view for now... Thoughts?

PS. Sorry for the delay. :)