bug: can't use async functions as resolvers

[aearly]

This doesn't work as expected:

fount.register('foo', async (config) => {
  var foo = await getFoo(config).catch(() =>  null)
  return foo
})

What is registered is the entire async function, rather than its resolved value, which is surprising.

Luckily, this is already fixed by #14 . Lodash 3's isFunction returns false for async functions, fauxdash's version works as expected.