general improvements (api breaking, v0.1.0)
- simplified naming
- move to store timestamps in seconds internally
- added Recorder, a simplified interface to record multiple
  sequential steps
- added XunitDestination, a class marshalling the creation of xml
  file under a root path, and checking if those files have actually
  been produced.
- new example in README
support unicode & xml entities in test reports
release 0.1.1
cleaner error representations
release 0.1.2