support `html` and `htmel` tagged template functions:

[sc0ttj]

• added src/html.js, to be integrated as an add-on (WIP)
• App.view() can now return HTML Objects (not only strings):
  • define a view func that returns an HTML Object, and it will now work OK (still renders, can be updated, etc)
• integrated the html.js and htmel.js scripts into build process
• update README to document its features and how to use it

TODO:

• update examples to use html and htmel
• update version numbers, re-publish