Fix: Optional methods are not marked as optional (fixes #206)

Author: Pajn

Diff for: lib/ast-converter.js

@@ -759,6 +759,7 @@ module.exports = function(ast, extra) {
                     SyntaxKind.Parameter === node.parent.kind ||
                     SyntaxKind.PropertyDeclaration === node.parent.kind ||
                     SyntaxKind.PropertySignature === node.parent.kind ||
+                    SyntaxKind.MethodDeclaration === node.parent.kind ||
                     SyntaxKind.MethodSignature === node.parent.kind
                 )) {
                     result.optional = true;