strconv: AppendFloat don't return OK boolean

JS: suppress checking for duplicate private members in classes, fixes…

… #932

JS: fix parsing objects in body of object-property-method by register…

…ing variables correctly

JS: add OpOpt for OptionalExpression and add precedence to CallExpr t…

…o fix precedence issues in the minifier

CSS: fix declaration errors

CSS: update parseDeclaration to parse nested rulesets

CSS: add hacky fix for nested rulesets

JS: parse private elements in classes as variables that can be renamed

CSS: fix parsing custom identifier tokens, such as --0

Merge pull request #126 from mjethani/feature/css-layers

CSS: support layer at-rule