Fix a bug where takeE n actually takes n-1 events

Without this fix, `test_takeE` fails:

```
% ghc -e "_unitTest" FRP/Ordrea.hs
### Failure in: 3                         
expected: [[1,2],[],[3]]
 but got: [[1,2],[],[]]
Cases: 4  Tried: 4  Errors: 0  Failures: 1
Counts {cases = 4, tried = 4, errors = 0, failures = 1}
it :: Counts
```

The patch also contains some fixes for the test script and the cabal file.