Fixed readme.txt.

Renamed level-design.txt to level_design.txt.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@3764 c06c8d41-db1a-0410-9941-cceddc491573

Created by  dploog  on March 20, 2008
O4IQ4YKZYB7K4WYVBGPRF43XFE54SJWCUPD7ERYTED22PDNCNUIAC
Change contents