Update sass_api to 3.0.0 (#226)

Author: jathak

lib/src/migration_visitor.dart

@@ -24,7 +24,8 @@ import 'patch.dart';
 /// If [migrateDependencies] is enabled, this visitor will construct and run a
 /// new instance of itself (using [newInstance]) each time it encounters an
 /// `@import` or `@use` rule.
-abstract class MigrationVisitor extends RecursiveAstVisitor {
+abstract class MigrationVisitor
+    with RecursiveStatementVisitor, RecursiveAstVisitor {
   /// A mapping from URLs to migrated contents for stylesheets already migrated.
   final _migrated = <Uri, String>{};
 

lib/src/migrators/module/references.dart

@@ -167,7 +167,7 @@ class References {
 }
 
 /// A visitor that builds a References object.
-class _ReferenceVisitor extends RecursiveAstVisitor {
+class _ReferenceVisitor with RecursiveStatementVisitor, RecursiveAstVisitor {
   final _variables = BidirectionalMap<VariableExpression, MemberDeclaration>();
   final _variableReassignments = BidirectionalMap<
       MemberDeclaration<VariableDeclaration>, MemberDeclaration>();

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass_migrator
-version: 1.5.6
+version: 1.5.7-dev
 description: A tool for running migrations on Sass files
 homepage: https://github.com/sass/migrator
 
@@ -10,14 +10,15 @@ dependencies:
   args: ^2.1.0
   charcode: ^1.2.0
   collection: ^1.16.0
-  file: ^6.1.0
+  # Workaround until pulyaevskiy/node-interop#110 is resolved
+  file: '>=6.1.0 <6.1.2'
   glob: ^2.0.1
   js: ^0.6.3
   meta: ^1.3.0
   node_interop: ^2.0.2
   node_io: ^2.1.0
   path: ^1.8.0
-  sass_api: ^1.0.0-beta.48
+  sass_api: ^3.0.0
   source_span: ^1.8.1
   string_scanner: ^1.1.0
   term_glyph: ^1.2.0