Superfluous newlines in description section lists items

[zdne]

Given

# API 

Before Hello

- a
- b

After Hello World

The output AST description node contains extraneous newlines after each list item.

Actual

_version: 2.0
metadata:
name: "API"
description: "Before Hello\n\n- a\n\n- b\n\nAfter Hello World\n"
resourceGroups:

[pksunkara]

Robotskirt is disregarding the extra newlines.

[abtris]

Migrated to apiaryio/drafter#641