Fix livereload issues by replacing it with Browser-Sync.

This PR removes livereload, as well as the `serve` and `open` tasks; Browser-Sync now provides these same features.

Additionally:
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The `build/` directory is now served, instead of `./`.
To facilitate that, a `copy` task was created.
To make that addition more reasonable in a seed/demo project, `index.html` was moved to `src/htdocs`.

Finally:
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Changed it so that task `watch` depends on task `build`.  This ensures that the build is done before the watcher starts; launching them both at the same time works, but it's kindof weird (clutters the console output, fires reloads on startup, etc.).

This means you cannot run `watch` without it also running `build`.  That could be a problem for larger projects.  I don't think it's a problem here, though.