Refactor Gruntfile to dev vs. dist builds

This sets the stage for better automated testing and consistency across
browser vs. CLI tests. I'm opening this PR now but I'm still planning on pushing more changes to it. Presently I'm setting up Browserify to run tests in the browser; following that we'll be able to get the tests running in different browsers. I'm hoping we can use SauceLabs or something similar that provides free testing for open source projects.

For the changes thus far, we can build just like before with a new command: `grunt build:dist`, but I've also provided a dev build that builds to `tmp` so we can develop without putting the changes in dist.

### Work Remaining

1. Setup browserify for CommonJS in the browser
2. Split out `src/Bacon.JQuery.Bindings.coffee` and `test/Bacon.JQuery.Bindings.Spec.coffee` into multiple smaller files
3. At the same time as splitting out files, Implement ES6 modules for easier switching if we want to do AMD/UMD compiles; and forward-compatible syntax
2. Use Karma or Testem via grunt for automating browser tests
3. Setup SauceLabs to run browser tests via travis

What do you think of this plan? I'm open to a simpler path if you have any other ideas.