Make SiteTree reference conditional

This makes the boilerplate code compatible for testing
framework-only sites.
Merge pull request #58 from oddnoc/safe-sitetree

Make SiteTree reference conditional in InitProcessor
API Support extended JS error reporting
Merge pull request #64 from tractorcow/pulls/stacktrace

API Support extended JS error reporting
Ensure that the window is maximised prior to running each step
Fixes #27: I wait until I see text/element
Inital changes to wait for text