improved error output
pull out simple_selector into two options for more granularity
pull apart pseudo_class syntax into more parts, accept any expr within pseudo_classes with parameters
corrected desired output for comma-separated selectors
remove debug comment
fix default vendorize option
better error messages for generic LyErrors
test for comma-separated selectors
better error messaging for prettified CSS with prefixr
differentiate between comma-separated selectors and space-separated selectors
simple_selectors = everything, including space-separated selectors, except for comma
complex_selectors = comma-separated simple_selectors
fix logic for combination and css output of selectors