pubspec tweaks (#18)

diff --git a/pubspec.yaml b/pubspec.yaml
index 8e40eb7..bb6937e 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,11 +1,11 @@
 name: http_io
-version: 0.10.0
+version: 0.10.0-dev
 author: "Dart Team <misc@dartlang.org>"
 homepage: https://github.com/dart-lang/http_io
 description: HTTP Client and Server APIs.
+environment:
+  sdk: ">=1.24.0 <2.0.0"
 dev_dependencies:
   convert: "^2.0.1"
   crypto: "^2.0.2+1"
   test: "^0.12.18"
-environment:
-  sdk: ">=1.24.0 <3.0.0"