Additional fixes for #565.

-   Escaped binding expressions.
-   Cleaned up wording a bit.
-   Tested code in jsbin and added some clarifications
    based on things that were confusing to me. (In particular, the second
    version of `<app-globals>` doesn't work with the previous
    `<my-component>`, and configuring the element with camelCase
    attributes is confusing because the actual property names end up lowercase.)
By the way, I can't see any good reason to copy here instead of adding accessors. This makes the globals look mutable, but in fact if you change the property values, you're only modifying the local copy.