Start implementing HFrame body transitions:
- specify `conditions`: "uninitialized loading loaded" and aliases
- conditions are used to select the appropriate body definition to render
    a particular phase of frame loading, hence    HFrameDefinition#render(doc, condition)
- if a HBodyDefinition has no child HTransformDefinition then it is assumed
    to be a null transform which just renders as its contents
    (ignoring any input). This is not appropriate for the `loaded` condition
- when navigation is requested (by clicking on a hyperlink)
    the targetted HFrame loading process now has a preload() phase which
    displays a "loading" body (if available)

Also implemented _.find()
preach() - promisified forEach/forOwn - is no longer used
HTMLLoader class is (mostly) refactored into httpProxy object.
    new HTMLLoader.load(method, url, data, details) ->
    httpProxy.load(url, { method: method, responseType: 'document')

Remove framer.options.load and HFrameDefinition.options.load.
Customized HTTP loading SHOULD NOT be a frame option.
Maybe something like ServiceWorker caches would be appropriate.