support latest pkg:build_runner (#165)

diff --git a/pubspec.yaml b/pubspec.yaml
index 8053517..6af1ddf 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: mockito
-version: 3.0.0
+version: 3.0.1-dev
 
 authors:
   - Dmitriy Fibulwinter <fibulwinter@gmail.com>
@@ -18,6 +18,6 @@
   test: ^1.2.0
 
 dev_dependencies:
-  build_runner: ^0.9.1
+  build_runner: ^1.0.0
   build_test: ^0.10.0
   build_web_compilers: ^0.4.0