Add possibility to define example of request body and request response.

This can be done by two new annotations:
- requestBody
- responseBody

Value for this new param can be string or path to file with the reponse text.
Tab as spaces fix
Merge branch 'feature/discriminator'
Support for michelf/php-markdown
Change test after changing to michelf/php-markdown
Merge pull request Add possibility to define example of request body and request response for endpoints. https://github.com/nelmio/NelmioApiDocBundle/pull/338

# By Michał Schroeder
# Via Michał Schroeder
* commit 'f170993ee32e8068901a6b5e851e017caa2e6a30':
  Change test after changing to michelf/php-markdown
  Support for michelf/php-markdown
  Tab as spaces fix
  Add possibility to define example of request body and request response.