Prepare to publish null-safe version (#38)

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index 32b9f13..fe71126 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,30 +1,12 @@
 language: dart
 
 dart:
-  - dev
+- dev
 
-jobs:
-  include:
-    - stage: analyze_and_format
-      name: "Analyze"
-      os: linux
-      script: dartanalyzer --enable-experiment=non-nullable --fatal-warnings --fatal-infos .
-    - stage: analyze_and_format
-      name: "Format"
-      os: linux
-      script: dartfmt -n --set-exit-if-changed .
-    - stage: test
-      name: "Vm Tests"
-      os: linux
-      script: pub run --enable-experiment=non-nullable test -p vm
-    - stage: test
-      name: "Web Tests"
-      os: linux
-      script: pub run --enable-experiment=non-nullable test -p chrome
-
-stages:
-  - analyze_and_format
-  - test
+dart_task:
+- dartfmt
+- dartanalyzer: --fatal-warnings --fatal-infos .
+- test: -p chrome,vm
 
 # Only building master means that we don't run two builds for each pull request.
 branches:
@@ -32,4 +14,4 @@
 
 cache:
   directories:
-    - $HOME/.pub-cache
+  - $HOME/.pub-cache

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2244742..0ade9ff 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,4 @@
-## 4.0.0-nullsafety-dev
+## 4.0.0-nullsafety
 
 * Migrate to null safety.
 

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
index 5db173f..9592540 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,15 +1,11 @@
 name: http_parser
-version: 3.2.0-nullsafety-dev
+version: 4.0.0-nullsafety
 description: >-
   A platform-independent package for parsing and serializing HTTP formats.
 homepage: https://github.com/dart-lang/http_parser
 
-# Unsafe to publish until null safety is stable or this package is in
-# the allow list
-publish_to: none
-
 environment:
-  sdk: '>=2.11.0-0 <2.12.0'
+  sdk: '>=2.12.0-0 <3.0.0'
 
 dependencies:
   charcode: ^1.2.0-nullsafety
@@ -21,3 +17,9 @@
 dev_dependencies:
   pedantic: ^1.10.0-nullsafety
   test: ^1.16.0-nullsafety.4
+
+# Because these packages depend on the prev4 version of this package
+dependency_overrides:
+  shelf: 0.7.9
+  shelf_static: 0.2.8
+  test: 1.16.0-nullsafety.9