Point Chartbeat readme link to actual homepage
Add useCanonical to options and _sf_async_config with default value true
Preserve existing _sf_async_config values unless overridden by via settings/defaults
Replace obsolete protocol-specific script load URLs with protocol-agnostic URL
Fix issue where Chartbeat script loads and executes before document.body exists

The Chartbeat script immediately accesses document.body on execution so it must
be sure document.body exists prior to loading.
Merge branch 'chartbeat-fixes' of https://github.com/dbow/analytics.js-integrations into dbow-chartbeat-fixes
Merge branch 'dbow-chartbeat-fixes'