ignore XJSEmptyExpression - fixes #214
add types.isDynamic so we can scan a node to see if it's ~safe~ to include it twice
Merge branch 'system' of github.com:guybedford/6to5 into guybedford-system
Merge branch 'guybedford-system'
Remove --no-timeouts flag.

Not a valid flag, causes errors when trying to use debug modes.
add 1.13.12 changelog
add VirtualPropertyExpression and SpreadProperty to ast-types
simplify generator context id
clean up Scope reference addition
remove SpreadProperty definition
temporarily disable es7-modules-system tests
v1.13.12
Merge pull request #218 from timoxley/no-no-timeouts

Remove --no-timeouts flag.
add 1.13.13 changelog
v1.13.13
remove irrelevant max line length
add playground
remove arguments-to-array helper
remove weird sounding however in playground warning message
clarify playground warning note