Only test oldest supported and dev + stable

Speed up travis times
diff --git a/.travis.yml b/.travis.yml
index df0d92c..d2c97e3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,6 @@
 dart:
   - dev
   - stable
-  - 1.22.1
   - 1.21.1
 cache:
   directories:
diff --git a/pubspec.yaml b/pubspec.yaml
index 7e20b41..c5920d6 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -4,6 +4,8 @@
 homepage: https://github.com/dart-lang/http_parser
 description: >
   A platform-independent package for parsing and serializing HTTP formats.
+environment:
+  sdk: ">=1.21.0 <2.0.0-dev.infinity"
 dependencies:
   charcode: "^1.1.0"
   collection: ">=0.9.1 <2.0.0"
@@ -12,5 +14,3 @@
   typed_data: "^1.1.0"
 dev_dependencies:
   test: "^0.12.0"
-environment:
-  sdk: ">=1.21.0 <2.0.0-dev.infinity"