Set version to v0.13.0-pre
Merge pull request #159 from apiaryio/zdne/bump-version

Set version to v0.13.0-pre
Merge pull request #160 from apiaryio/pksunkara/refactor

Unexpected nodes with keywords will not stop the parsing
Recognize body with content on its signature
Fix warning messages when abbreviated payloads
Recognize Parameters with non-recognized no newline parameter
Parameters can be a description of Payload