Changing PHP memory_limit from 512M to 192M

For most sites, the default value of PHP is fine (128M) but it's good to have higher to make sure almost no one has issues for normal use. If more than 192M is required, it's likely an issue in the script which should be fixed.
Merge pull request #3 from marclaporte/patch-2

Changing PHP memory_limit from 512M to 192M