enabled slf4j and setup default log files for tests

sets up slf4j and default log files when running tests.

For example, when running Live tests, `target/test-data/jclouds-wire.log` will contain http traffic generated from the provider.

Ex. logs created during ultradns tests
```
./providers/denominator-ultradns/target/test-data/jclouds-wire.log
./providers/denominator-ultradns/target/test-data/jclouds.log
```