Move browserify dep to devDependencies and note global transforms.

I think it's important to note that you may want to run requireify as a global transform so you can e.g. `require('jquery')` in the console. If it doesn't run as a global transform it will not pick up any module in `node_modules`. This is also mandatory if you're symlinking your frontend folders for easier `require`ing.

Additionally I moved `browserify` to `devDependencies` as is the convention in other browserify transforms. No need to gum up people's `node_modules` folders with another copy of browserify.