Update fixtures to AST serialization v2.0
Set AST_SERIALIZATION_VERSION to 2.0
Rename targets
Update YAML serialization to v2.0
Add ./tmp to gitignore
Update JSON serialization to v2.0
Deprecate resource and action section headers
Add real deprecation warnings, modify aruba PATH env
Extend use section of README
Merge pull request #80 from apiaryio/develop

Breaking: Implement AST media types v2.0, deprecate resource and action section's headers