fly-esnext not applied

Nobody has claimed this yet.

Hi,

I get this error after a fresh install:

```sh
> @ dev /Users/ngryman/Projects/noflash
> fly

stack:
- ~/Projects/noflash/flyfile.js:1
- (function (exports, require, module, __filename, __dirname) { import browserify from 'browserify'
- ^^^^^^
- SyntaxError: Unexpected token import
- at Object.exports.runInThisContext (vm.js 76:16)
- at Module._compile (module.js 528:28)
- at Object.Module._extensions..js (module.js 565:10)
- at Module.load (module.js 473:32)
- at tryModuleLoad (module.js 432:12)
- at Function.Module._load (module.js 424:3)
- at Module.require (module.js 483:17)
- at require (internal/module.js 20:19)
- at new Fly (~/Projects/noflash/node_modules/fly/lib/index.js 19:43)
- at Object. (~/Projects/noflash/node_modules/fly/lib/cli/spawn.js 37:9)
- at next (native)
- at tryCatcher (~/Projects/noflash/node_modules/bluebird/js/release/util.js 16:23)
- at PromiseSpawn._promiseFulfilled (~/Projects/noflash/node_modules/bluebird/js/release/generators.js 97:49)
- at Promise._settlePromise (~/Projects/noflash/node_modules/bluebird/js/release/promise.js 572:26)
- at Promise._settlePromise0 (~/Projects/noflash/node_modules/bluebird/js/release/promise.js 612:10)
- at Promise._settlePromises (~/Projects/noflash/node_modules/bluebird/js/release/promise.js 691:18)
message: Unexpected token import
```

I'm running `fly` through a `npm` `run-script`.

I've got the following fly packages as dependencies:
```json
{
"fly": "beta",
"fly-autoprefixer": "^1.0.0",
"fly-browserify2": "^2.0.1",
"fly-esnext": "^2.0.0",
"fly-sass": "^2.0.0"
}
```

Node version is `6.5.0`.

Thanks!

Reproduce the fresh install with Node 6.5.0 through an npm run-script, using the listed Fly packages and flyfile.js. Start with flyfile.js and the Fly entry points shown in fly/lib/index.js and fly/lib/cli/spawn.js, then verify that the import syntax error no longer occurs and fly-esnext is applied.

Written by the indexing model from the issue text.