Remove reference to nonexistent constants module

[JimRottinger]

See title. Addresses #3. It was throwing the following error before this change.

Error: Cannot find module '../constants'
    at Function.Module._resolveFilename (module.js:325:15)
    at Function.Module._load (module.js:276:25)
    at Module.require (module.js:353:17)
    at require (internal/module.js:12:17)
    at Object.<anonymous> (/Users/looker/Looker/dataflux-example/build/server/middleware.coffee:7:18)
    at Object.<anonymous> (/Users/looker/Looker/dataflux-example/build/server/middleware.coffee:6:1)
    at Module._compile (module.js:409:26)
    at Object.loadFile (/Users/looker/.nvm/versions/node/v4.7.0/lib/node_modules/coffee-script/lib/coffee-script/register.js:16:19)
    at Module.load (/Users/looker/.nvm/versions/node/v4.7.0/lib/node_modules/coffee-script/lib/coffee-script/register.js:45:36)
    at Function.Module._load (module.js:300:12)
    at Module.require (module.js:353:17)
    at require (internal/module.js:12:17)
    at Object.<anonymous> (/Users/looker/Looker/dataflux-example/build/server/server.coffee:8:14)
    at Object.<anonymous> (/Users/looker/Looker/dataflux-example/build/server/server.coffee:6:1)
    at Module._compile (module.js:409:26)
    at Object.exports.run (/Users/looker/.nvm/versions/node/v4.7.0/lib/node_modules/coffee-script/lib/coffee-script/coffee-script.js:173:23)
    at compileScript (/Users/looker/.nvm/versions/node/v4.7.0/lib/node_modules/coffee-script/lib/coffee-script/command.js:224:29)
    at compilePath (/Users/looker/.nvm/versions/node/v4.7.0/lib/node_modules/coffee-script/lib/coffee-script/command.js:174:14)
    at Object.exports.run (/Users/looker/.nvm/versions/node/v4.7.0/lib/node_modules/coffee-script/lib/coffee-script/command.js:98:20)
    at Object.<anonymous> (/Users/looker/.nvm/versions/node/v4.7.0/lib/node_modules/coffee-script/bin/coffee:15:45)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Function.Module.runMain (module.js:441:10)
    at startup (node.js:139:18)
    at node.js:990:3

[nodemon] app crashed - waiting for file changes before starting...