Fixing XML ending tags

XML tags will never start and end with '</' and '/>'.

Also adjusted the testsuites tag call to use the function call properly
which ends the tag as expected.

Results: 

```
<testsuites>
    <testsuite name="Mocha Tests" tests="7" failures="0" errors="0" skip="0" timestamp="Wed, 12 Nov 2014 02:49:13 GMT" time="2.758">
        <testcase classname="mocha: .Users.jon.base.coursera.site.app.www.static.pages.open-course.test.mocha.peerReview.views.preview: open-course peerReview views preview" name="appends review view" time="0.001" />
        <testcase classname="mocha: .Users.jon.base.coursera.site.app.www.static.pages.open-course.test.mocha.peerReview.views.preview: open-course peerReview views preview" name="appends alerts view" time="0" />
        <testcase classname="mocha: .Users.jon.base.coursera.site.app.www.static.pages.open-course.test.mocha.peerReview.views.preview: open-course peerReview views preview" name="appends SubmissionHeader view" time="0" />
        <testcase classname="mocha: .Users.jon.base.coursera.site.app.www.static.pages.open-course.test.mocha.peerReview.views.preview: open-course peerReview views preview" name="has an edit button that links to the edit page" time="0.002" />
        <testcase classname="mocha: .Users.jon.base.coursera.site.app.www.static.pages.open-course.test.mocha.peerReview.views.preview: open-course peerReview views preview" name="submits" time="0.012" />
        <testcase classname="mocha: .Users.jon.base.coursera.site.app.www.static.pages.open-course.test.mocha.peerReview.views.preview: open-course peerReview views preview" name="handles unknown submit errors" time="0.015" />
        <testcase classname="mocha: .Users.jon.base.coursera.site.app.www.static.pages.open-course.test.mocha.peerReview.views.preview: open-course peerReview views preview" name="handles invalid submission errors" time="0.013" />
    </testsuite>
</testsuites>
```
i'm just moving your code from line 61 up here, but this is a function that's declared [here](https://github.com/coursera/triple-latte/blob/jw/fix-xml/lib/xunit.js#L75-L100)