Fix Cobertura coverage array

[ale7714]

Cobertura formatter is currently working under the assumption that the coverage tool is gonna report lines ordered by number and without duplicate line numbers. This causes that for coverage data that looks like this:

<package name="" line-rate="1.0" branch-rate="1.0" complexity="1.0">
  <classes>
    <class name="Main" filename="Main.java" line-rate="1.0" branch-rate="1.0" complexity="1.0">
      <lines>
        <line number="4" hits="8" branch="false" />
        <line number="2" hits="4" branch="false" />
        <line number="4" hits="1" branch="false" />
        <line number="1" hits="6" branch="false" />
      </lines>
    </class>
  </classes>
</package>

We're going to incorrectly report a coverage array of [0, 0, 0, 8, 4,1,6]. And we should report [6, 4, nil,9]

This PR addresses this issues by:

• Sorting lines by number before building the coverage array
• For lines with the same number, we're going to sum the hits

[maxjacobson]

LGTM

Just wondering, does the test reporter support go yet? If so, we should hook it up :)

[ABaldwinHunter]

Nice fix

[ale7714]

@maxjacobson yes and yes! We should make sometime to do this :)