Change definition of summary/description break

In this commit I have made the following documentation changes:

- Changed short description to summary
- Changed long description to description
- Changed example mail address
- Changed definition when a summary breaks and becomes a description
  to match PSR-5 and actual usage.

See: https://github.com/phpDocumentor/ReflectionDocBlock/issues/34#issuecomment-49510977
I have changed the text to be more clear