I installed bcoin and I get this error about the version:

$ node -v
v8.2.1
$ npm -v
5.3.0
$ bcoin
/usr/lib/node_modules/bcoin/lib/db/backends.js:26
    throw e;
     ^
Error: The module '/usr/lib/node_modules/bcoin/node_modules/leveldown/build/Release/leveldown.node'
was compiled against a different Node.js version using
NODE_MODULE_VERSION 48. This version of Node.js requires
NODE_MODULE_VERSION 57. Please try re-compiling or re-installing
the module (for instance, using `npm rebuild` or `npm install`).
    at Object.Module._extensions..node (module.js:598:18)
    at Module.load (module.js:503:32)
    at tryModuleLoad (module.js:466:12)
    at Function.Module._load (module.js:458:3)
    at Module.require (module.js:513:17)
    at require (internal/module.js:11:18)
    at bindings (/usr/lib/node_modules/bcoin/node_modules/leveldown/node_modules/bindings/bindings.js:76:44)
    at Object.<anonymous> (/usr/lib/node_modules/bcoin/node_modules/leveldown/leveldown.js:4:46)
    at Module._compile (module.js:569:30)
    at Object.Module._extensions..js (module.js:580:10)

any ideas why?