Dart format with latest SDK (#90)

Also fix dependencies
diff --git a/lib/src/http_exception.dart b/lib/src/http_exception.dart
index 4330afa..d67472e 100644
--- a/lib/src/http_exception.dart
+++ b/lib/src/http_exception.dart
@@ -11,7 +11,9 @@
   const HttpException(this.message, {this.uri});
 
   String toString() {
-    var b = StringBuffer()..write('HttpException: ')..write(message);
+    var b = StringBuffer()
+      ..write('HttpException: ')
+      ..write(message);
     if (uri != null) {
       b.write(', uri = $uri');
     }
diff --git a/lib/src/http_headers_impl.dart b/lib/src/http_headers_impl.dart
index b0e8242..6e04eda 100644
--- a/lib/src/http_headers_impl.dart
+++ b/lib/src/http_headers_impl.dart
@@ -503,14 +503,19 @@
   String toString() {
     StringBuffer sb = StringBuffer();
     headers.forEach((String name, List<String> values) {
-      sb..write(name)..write(": ");
+      sb
+        ..write(name)
+        ..write(": ");
       bool fold = _foldHeader(name);
       for (int i = 0; i < values.length; i++) {
         if (i > 0) {
           if (fold) {
             sb.write(", ");
           } else {
-            sb..write("\n")..write(name)..write(": ");
+            sb
+              ..write("\n")
+              ..write(name)
+              ..write(": ");
           }
         }
         sb.write(values[i]);
@@ -654,7 +659,11 @@
     sb.write(_value);
     if (parameters != null && parameters.isNotEmpty) {
       _parameters.forEach((String name, String value) {
-        sb..write("; ")..write(name)..write("=")..write(value);
+        sb
+          ..write("; ")
+          ..write(name)
+          ..write("=")
+          ..write(value);
       });
     }
     return sb.toString();
@@ -936,18 +945,29 @@
 
   String toString() {
     StringBuffer sb = StringBuffer();
-    sb..write(name)..write("=")..write(value);
+    sb
+      ..write(name)
+      ..write("=")
+      ..write(value);
     if (expires != null) {
-      sb..write("; Expires=")..write(HttpDate.format(expires));
+      sb
+        ..write("; Expires=")
+        ..write(HttpDate.format(expires));
     }
     if (maxAge != null) {
-      sb..write("; Max-Age=")..write(maxAge);
+      sb
+        ..write("; Max-Age=")
+        ..write(maxAge);
     }
     if (domain != null) {
-      sb..write("; Domain=")..write(domain);
+      sb
+        ..write("; Domain=")
+        ..write(domain);
     }
     if (path != null) {
-      sb..write("; Path=")..write(path);
+      sb
+        ..write("; Path=")
+        ..write(path);
     }
     if (secure) sb.write("; Secure");
     if (httpOnly) sb.write("; HttpOnly");
diff --git a/lib/src/http_impl.dart b/lib/src/http_impl.dart
index 4f74002..50f9f11 100644
--- a/lib/src/http_impl.dart
+++ b/lib/src/http_impl.dart
@@ -1074,7 +1074,10 @@
       StringBuffer sb = StringBuffer();
       for (int i = 0; i < cookies.length; i++) {
         if (i > 0) sb.write("; ");
-        sb..write(cookies[i].name)..write("=")..write(cookies[i].value);
+        sb
+          ..write(cookies[i].name)
+          ..write("=")
+          ..write(cookies[i].value);
       }
       headers.add(HttpHeaders.COOKIE, sb.toString());
     }
@@ -2931,7 +2934,9 @@
     String qop;
     String cnonce;
     String nc;
-    hasher = MD5()..add(credentials.ha1.codeUnits)..add([CharCode.COLON]);
+    hasher = MD5()
+      ..add(credentials.ha1.codeUnits)
+      ..add([CharCode.COLON]);
     if (credentials.qop == "auth") {
       qop = credentials.qop;
       cnonce = CryptoUtils.bytesToHex(CryptoUtils.getRandomBytes(4));
diff --git a/pubspec.yaml b/pubspec.yaml
index a5606ab..15d2069 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -8,7 +8,7 @@
   sdk: ">=2.8.4 <3.0.0"
 
 dev_dependencies:
-  convert: ^2.0.1
-  crypto: ^2.0.2+1
+  convert: '>=2.1.1 <4.0.0'
+  crypto: '>=2.1.5 <4.0.0'
   pedantic: ^1.0.0
   test: ^1.0.0