Move testing files to playground folder

diff --git a/comments_2018-06-28/.gitkeep b/playground/.gitkeep
similarity index 100%
rename from comments_2018-06-28/.gitkeep
rename to playground/.gitkeep

diff --git a/comments_2018-06-28/me.md b/playground/me.md
similarity index 100%
rename from comments_2018-06-28/me.md
rename to playground/me.md

diff --git a/comments_2018-06-28/phsw.txt b/playground/phsw.txt
similarity index 100%
rename from comments_2018-06-28/phsw.txt
rename to playground/phsw.txt

diff --git a/comments_2018-06-28/soubor.txt b/playground/soubor.txt
similarity index 100%
rename from comments_2018-06-28/soubor.txt
rename to playground/soubor.txt