Use test_api instead of test (#120)

This will get rid of transitive dep on test package for flutter_tools.

I also updated some deprecated member use and some various style stuff from Flutter's analysis options - I was going to do that for the file package as well but that's a bigger chore. If we'd rather have it all in one PR I can do that though.
diff --git a/packages/file_testing/CHANGELOG.md b/packages/file_testing/CHANGELOG.md
index 09ce81f..ee6e2be 100644
--- a/packages/file_testing/CHANGELOG.md
+++ b/packages/file_testing/CHANGELOG.md
@@ -1,3 +1,9 @@
+#### 2.1.0
+
+* Changed dependency on `package:test` to `package:test_api`
+* Bumped Dart SDK constraint to match `package:test_api`'s requirements
+* Updated style to match latest lint rules from Flutter repo.
+
 #### 2.0.3
 
 * Relaxed constraints on `package:test`
diff --git a/packages/file_testing/lib/src/testing/core_matchers.dart b/packages/file_testing/lib/src/testing/core_matchers.dart
index 58e11d3..adce554 100644
--- a/packages/file_testing/lib/src/testing/core_matchers.dart
+++ b/packages/file_testing/lib/src/testing/core_matchers.dart
@@ -4,31 +4,31 @@
 
 import 'dart:io';
 
-import 'package:test/test.dart';
+import 'package:test_api/test_api.dart';
 
 import 'internal.dart';
 
 /// Matcher that successfully matches against any instance of [Directory].
-const Matcher isDirectory = const isInstanceOf<Directory>();
+const Matcher isDirectory = TypeMatcher<Directory>();
 
 /// Matcher that successfully matches against any instance of [File].
-const Matcher isFile = const isInstanceOf<File>();
+const Matcher isFile = TypeMatcher<File>();
 
 /// Matcher that successfully matches against any instance of [Link].
-const Matcher isLink = const isInstanceOf<Link>();
+const Matcher isLink = TypeMatcher<Link>();
 
 /// Matcher that successfully matches against any instance of
 /// [FileSystemEntity].
-const Matcher isFileSystemEntity = const isInstanceOf<FileSystemEntity>();
+const Matcher isFileSystemEntity = TypeMatcher<FileSystemEntity>();
 
 /// Matcher that successfully matches against any instance of [FileStat].
-const Matcher isFileStat = const isInstanceOf<FileStat>();
+const Matcher isFileStat = TypeMatcher<FileStat>();
 
 /// Returns a [Matcher] that matches [path] against an entity's path.
 ///
 /// [path] may be a String, a predicate function, or a [Matcher]. If it is
 /// a String, it will be wrapped in an equality matcher.
-Matcher hasPath(dynamic path) => new _HasPath(path);
+Matcher hasPath(dynamic path) => _HasPath(path);
 
 /// Returns a [Matcher] that successfully matches against an instance of
 /// [FileSystemException].
@@ -39,7 +39,7 @@
 /// [osErrorCode] may be an `int`, a predicate function, or a [Matcher]. If it
 /// is an `int`, it will be wrapped in an equality matcher.
 Matcher isFileSystemException([dynamic osErrorCode]) =>
-    new _FileSystemException(osErrorCode);
+    _FileSystemException(osErrorCode);
 
 /// Returns a matcher that successfully matches against a future or function
 /// that throws a [FileSystemException].
@@ -67,14 +67,14 @@
 
 /// Matcher that successfully matches against a [FileSystemEntity] that
 /// exists ([FileSystemEntity.existsSync] returns true).
-const Matcher exists = const _Exists();
+const Matcher exists = _Exists();
 
 class _FileSystemException extends Matcher {
-  final Matcher _matcher;
-
   _FileSystemException(dynamic osErrorCode)
       : _matcher = _wrapMatcher(osErrorCode);
 
+  final Matcher _matcher;
+
   static Matcher _wrapMatcher(dynamic osErrorCode) {
     if (osErrorCode == null) {
       return null;
@@ -85,8 +85,8 @@
   @override
   bool matches(dynamic item, Map<dynamic, dynamic> matchState) {
     if (item is FileSystemException) {
-      return (_matcher == null ||
-          _matcher.matches(item.osError?.errorCode, matchState));
+      return _matcher == null ||
+          _matcher.matches(item.osError?.errorCode, matchState);
     }
     return false;
   }
@@ -103,10 +103,10 @@
 }
 
 class _HasPath extends Matcher {
-  final Matcher _matcher;
-
   _HasPath(dynamic path) : _matcher = wrapMatcher(path);
 
+  final Matcher _matcher;
+
   @override
   bool matches(dynamic item, Map<dynamic, dynamic> matchState) =>
       _matcher.matches(item.path, matchState);
@@ -125,7 +125,7 @@
     bool verbose,
   ) {
     desc.add('has path: \'${item.path}\'').add('\n   Which: ');
-    Description pathDesc = new StringDescription();
+    final Description pathDesc = StringDescription();
     _matcher.describeMismatch(item.path, pathDesc, matchState, verbose);
     desc.add(pathDesc.toString());
     return desc;
diff --git a/packages/file_testing/pubspec.yaml b/packages/file_testing/pubspec.yaml
index 1960a4e..8da2eb7 100644
--- a/packages/file_testing/pubspec.yaml
+++ b/packages/file_testing/pubspec.yaml
@@ -1,5 +1,5 @@
 name: file_testing
-version: 2.0.3
+version: 2.1.0
 authors:
 - Todd Volkert <tvolkert@google.com>
 description: Testing utilities for package:file
@@ -7,7 +7,7 @@
 
 dependencies:
   meta: ^1.1.2
-  test: '>=1.0.0 <2.0.0'
+  test_api: ^0.2.2
 
 environment:
-  sdk: '>=2.0.0-dev.28.0 <3.0.0'
+  sdk: '>=2.1.0 <3.0.0'