Allow customizing the driver repository for travis-ci
Allow customizing the driver repository for travis-ci

mongodb/mongo-php-library,jmikola/mongo-php-library,jmikola/mongo-php-library-prototype,mongodb/mongo-php-library,jmikola/mongo-php-library,mongodb/mongo-php-library,mongodb/mongo-php-library,10gen-labs/mongo-php-library-prototype,jmikola/mongo-php-library,jmikola/mongo-php-library