Make use of ParseResultRef in arguments for lazy referencing functions
currect lazy referencing structure
fix comment and remove MarkdownNodeIterator from input
Merge pull request #237 from alikh31/alikh31/lazyreferencing

Correct Lazy Referencing
Prepare for v0.15.1 release
Merge pull request #239 from apiaryio/zdne/release-v0.15.1

Prepare for v0.15.1 release