Allow "junit" format to be used for reports

```
grunt.initConfig({
  search: {
    junit: {
      options: {
        logFile: "path/to/junit-report.xml",
        logFormat: "junit"
      }
    }
  }
}
```
move generated test arthefacts out of Git control
Merge pull request #1 from yavorskiy/master

`logFile: 'junit'` format for JUnit XML output