Merge branch 'release/2.1.2' into develop
Update README.md [ci skip]
Adjusted case of true/false/null.
Updated to archer 0.4.1.
Minor documentation improvements.
Added Isolator::className() (fixes #10)
Updated changelog style [ci skip]
Added isolator trait (fixes #13)
Disabled trait test in PHP v5.3.
PSR compliance [ci skip]
Added test for pass-by-reference to generator.
Updated changelog.
Merge branch 'release/2.2.0'