Markdown filter: Newlines lost in YAML metadata

Created by: ccudennec-24t

Hi everyone!

When evaluating the new Markdown filter of 0.36-SNAPSHOT we came across a bug concerning YAML metadata: All newlines get lost after translation.

Example input:

#!markdown
---

title: Back to the future

year: 1985
---

Back to the Future is a 1985 American science fiction film directed by Robert Zemeckis and written by Zemeckis and Bob Gale.

Output of the filter's writer:

#!markdown
---title: Back to the futuretitle: year: 1985year: ---
Back to the Future is a 1985 American science fiction film directed by Robert Zemeckis and written by Zemeckis and Bob Gale.

You can take a look at the following commit to get a JUnit test for reproducing the problem: https://bitbucket.org/24t/okapi/commits/61956bbea6fa89e6ce410f0618da6a0542adfe1c?at=markdown-filter-yaml-header