Minimal EMMA XML report support.

Creates `coverage.xml` in the output directory; coverage by class
or method are not properly filled, forms translate as blocks and
lines are obvious.

For lines the percentage is calculated as covered vs. instrumented.

The total number of forms is mapped to `/report/stats/methods[value]`.
avoid division by zero
Use `data.xml` for proper xml generation.

Feels a lot cleaner :-)
Merge pull request #24 from undernorthernsky/master

Emma report format