Print reports to stdout

[alxndrsn]

Implements outputting of the error reports to standard output. This gives useful output from the plugin on Travis CI, where the XML and HTML output can't be easily accessed.

If this looks useful there is a bit of cleanup that could obviously done:

• allow disabling of this feature (likely it should be off by default)
• make variable and file names a bit clearer to differentiate between stdout and HTML transformations

Issue: #20