update for the 2.10 dev sdk (#231)

This is in preparation for the actual 2.10 dev sdk release. This package needs to be published and pinned in flutter simultaneously with that release.
diff --git a/.travis.yml b/.travis.yml
index d565606..781bdf2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,13 +1,13 @@
 language: dart
 
 dart:
-  - dev
+  - preview/raw/2.10.0-0.2-dev
 
 script: ./tool/travis.sh
 
 # Only building master means that we don't run two builds for each pull request.
 branches:
-  only: [master, null_safety]
+  only: [master]
 
 cache:
   directories:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 88040ff..84ca54c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## v 2.1.0-nullsafety.2
+
+* Update for the 2.10 dev sdk.
+
 ## v 2.1.0-nullsafety.1
 
 * Allow the <=2.9.10 stable sdks.
diff --git a/pubspec.yaml b/pubspec.yaml
index a1b01f6..1802ede 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,12 +1,11 @@
 name: vector_math
-version: 2.1.0-nullsafety.1
+version: 2.1.0-nullsafety.2
 description: A Vector Math library for 2D and 3D applications.
 homepage: https://github.com/google/vector_math.dart
 
 environment:
-  # This must remain a tight constraint (only allow dev versions) until nnbd is
-  # stable.
-  sdk: '>=2.9.0-18.0 <=2.9.10'
+  # This must remain a tight constraint until nnbd is stable
+  sdk: '>=2.10.0-0 <2.10.0'
 
 dev_dependencies:
   benchmark_harness: any
@@ -31,12 +30,14 @@
     git:
       url: git://github.com/dart-lang/sdk.git
       path: pkg/js
+      ref: 2-10-pkgs
   matcher:
     git: git://github.com/dart-lang/matcher.git
   meta:
     git:
       url: git://github.com/dart-lang/sdk.git
       path: pkg/meta
+      ref: 2-10-pkgs
   path:
     git: git://github.com/dart-lang/path.git
   pedantic: