fix browserifyability
fix browserifyability

calvinmetcalf/SQLdown,ralphtheninja/abstract-leveldown,bryce-gibson/SQLdown,shimonenator/couchbasedown,snowyu/node-abstract-nosql,ralphtheninja/abstract-leveldown,Level/abstract-leveldown,bigeasy/abstract-leveldown,watson/abstract-leveldown,calvinmetcalf/SQLdown,bryce-gibson/SQLdown