coverage and progress reporters combined show wrong line number on error

with

```
reporters: ['progress']
```

my error line number is well reported

```
PhantomJS 1.9.7 (Linux) ERROR
ReferenceError: Can't find variable: isArray
at /home/webskin/???.js:741
```

but with

```
reporters: ['coverage', 'progress']
```

I get

```
PhantomJS 1.9.7 (Linux) ERROR
ReferenceError: Can't find variable: isArray
at /home/webskin/???.js:9
```

Line number `9` is wrong

My tests are written in coffee and my tested files are written in js

Start by reproducing the issue with reporters set first to ['progress'] and then to ['coverage', 'progress'], using CoffeeScript tests against JavaScript files. Trace the coverage and progress reporter interaction and verify that the combined configuration reports the actual error line, such as 741 rather than 9.

Written by the indexing model from the issue text.