Add option --dry-run to check if JSON file is well-formed without modifying it.
BUMP-VERSION: 0.2.2 (was: 0.2.1)
FIX problem when current_feature was not initialized.
Issue #161: JSONFormatter: Should use a slightly different output schema.
RELATED CHANGES:

  * Add JSON schema for behave: etc/json/behave.json.schema
  * Add JSON schema validator utility script: bin/jsonschema_validate.py
  * JSON: Use JSON array mode now.
  * JSON: Added "type" to Background, Scenario, ScenerioOutline.
  * JSON: Added "error_message" to result.
  * JSON: Use now list<lines> instead of string for multi-line text