Might want to disable sourcemap for dist

[shaohua]

{"version":3,"file":"runtime.min.js","sources":["bower_components/requestAnimationFrame-polyfill/requestAnimationFrame.js","bower_components/promise-polyfill/Promise.js","bower_components/customevent-polyfill/customevent-polyfill.js","bower_components/WeakMap/weakmap.js","bower_components/MutationObservers/MutationObserver.js","bower_components/CustomElements/src/scope.js","bower_components/CustomElements/src/Observer.js","bower_components/CustomElements/src/CustomElements.js","bower_components/CustomElements/src/Parser.js","bower_components/CustomElements/src/boot.js","bower_components/html-template-polyfill/html-template-polyfill.js","bower_components/HTMLImports/src/scope.js","bower_components/HTMLImports/src/Loader.js","bower_components/HTMLImports/src/Parser.js","bower_components/HTMLImports/src/HTMLImports.js","bower_components/HTMLImports/src/Observer.js","bower_components/HTMLImports/src/boot.js"]

As a gadget developer who uses this repo, he/she might not have those bower_components installed.

Currently, this gives tons of errors in Safari:

[shaohua]

Ref: brunch/brunch#645