install-wp-tests.sh svn wget https wordpress.org

Use https for requests to wordpress.org   Fixes svn checkout currently failing using http like:

svn co --quiet http://develop.svn.wordpress.org/trunk/tests/phpunit/includes/
svn: E175002: Unable to connect to a repository at URL 'http://develop.svn.wordpress.org/trunk/tests/phpunit/includes'

github issue wp-cli/wp-cli#1529