Add caching of source line fetching
Add caching of source line fetching

kelunik/php-code-coverage,theseer/php-code-coverage,sebastianbergmann/php-code-coverage,theseer/php-code-coverage,Koc/php-code-coverage,theseer/php-code-coverage,iFixit/php-code-coverage,sebastianbergmann/php-code-coverage,sebastianbergmann/php-code-coverage