Code coverage information is now gathered via phpdbg (a separate executable) by if available rather than xdebug, as the latter is hard to turn on and off.
A "test:quick" task has also been added to Robo, which excludes 31 tests which together account for almost two thirds of the test run time. This should pave the way for testing to be added as a commit hook for Git.
The plan had originally been to use Bldr, but Bldr's features were not particularly compelling, and it has not been maintained recently. By contrast Robo has very useful features while still meeting my needs.
In addition to migrating the build process, the current Robo file also runs unit tests, with or without coverage reporting.
Fixes #116; improves #113
