Remove React.autoBind entirely
Rename `BrowserEnv` to `ViewportMetrics`

Becuase that's what it is.
Restore @spicyj's lifecycle tests

These got lost in a rebase.
Use ReactID.ATTR_NAME as the React-specific ID attribute name.

Another step in the plan towards making `ReactID.ATTR_NAME` the central
source of truth regarding the React-specific ID attribute name.