Merge pull request #27 from ruda/test_result_junit

plugins.xunit: Add class XmlResult.
Merge pull request #28 from ruda/test_result_junit

avocado.plugins.xunit: Documentation.
docs: Updating GetStartedGuide

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
docs: Improving Introduction

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
docs: Improving WritingTests

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #29 from avocado-framework/documentation

Documentation
avocado.plugins.xunit: Cosmetic fixes in documentation.

Signed-off-by: Ruda Moura <rmoura@redhat.com>