Adding TAP output support

In order to integrate with automated systems, it's useful for drive to be able to speak a standard test output language.

[TAP](http://testanything.org/wiki/index.php/Main_Page) seems like a good choice as it is well-documented, simple, supported by Jenkins (with a plugin), and isn't XML.

A typical run would look like:

```
1..4
## test suite 1
ok 1 - first test
ok 2 - second test
not ok 3 - third test
## test suite 2
ok 4 - suite 2's first test
```