need to quote strings for ini_set()

Experienced the following errors when using the ini() array in the config.yml being compiled into settings.php:
`Parse error: syntax error, unexpected 'M' (T_STRING) in /var/www/sites/cmog.dev/cnf/settings.php on line 14`

my `config.yml` looks like:

        ini: {memory_limit: "256M"}

So, rather than doing something silly like: 

        ini: {"'memory_limit'": "'256M'"}

I've patched the compiler to add single quotes to the `ini_set()` argument strings.