Error message if browserify is not installed

[limikael]

For some reason I have beefy in my devDependencies but not browserify. Naturally things didn't work for me after doing and npm install on a new machine. That's expected. But the error message I got was a little confusing:

listening on http://localhost:8001/
200   19ms      886B /index.html

events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: spawn ENOENT
    at errnoException (child_process.js:980:11)
    at Process.ChildProcess._handle.onexit (child_process.js:771:34)
npm ERR! weird error 8
npm ERR! not ok code 0

Since this could often be a "first impression" of the beefy workflow for people it would be nice if the message was a bit more informative. In my min it would be as simple as typing out a message saying that the user needs to install browserify. I'm happy to fix this issue by adding such a message if no one objects...

[mikolalysenko]

Maybe browserify should be moved to a dependency and installed locally?

[gingermusketeer]

Looks like there is a different issue now that 2.0 is out. If a bundler is missing then there is no error message. I think the err here https://github.com/chrisdickinson/beefy/blob/master/bin/beefy#L12 just needs to be logged