Corrected readme.txt installation instructions

git-svn-id: https://plugins.svn.wordpress.org/qlikview-syntax-highlighter/trunk@1015220 b8457f37-d9ea-0310-8a92-e5e31aec5664
Corrected issue with readme.txt install instructions. Previous attempt to correct the issue failed.

git-svn-id: https://plugins.svn.wordpress.org/qlikview-syntax-highlighter/trunk@1015224 b8457f37-d9ea-0310-8a92-e5e31aec5664