Added a changelog

CHANGELOG.md

@@ -0,0 +1,12 @@
+# Change Log
+All notable changes to this project will be documented in this file.
+Please keep to the changelog format described on [keepachangelog.com](http://keepachangelog.com).
+This project adheres to [Semantic Versioning](http://semver.org/).
+
+## [Unreleased]
+### Added
+- Added a changelog
+
+### Changed
+- Made validation failures raise a `JSON::Schema::SchemaParseError` and data
+  loading failures a `JSON::Schema::JsonLoadError`

CONTRIBUTING.md

@@ -2,6 +2,6 @@ The Ruby JSON Schema library is meant to be a community effort, and as such, the
 
 All individuals that have a pull request merged will receive collaborator access to the repository. Due to the restrictions on RubyGems authentication, permissions to release a gem must be requested along with the email desired to be associated with the release credentials.
 
-Accepting changes to the JSON Schema library shall be made through the use of pull requests on GitHub. A pull request must receive at least two (2) "+1" comments from current contributors to the JSON Schema library before being accepted and merged. If a breaking issue and fix exists, please feel free to contact the project maintainer at [email protected] or @hoxworth for faster resolution.
+Accepting changes to the JSON Schema library shall be made through the use of pull requests on GitHub. A pull request must receive at least two (2) "+1" comments from current contributors, and include a relevant changelog entry, before being accepted and merged. If a breaking issue and fix exists, please feel free to contact the project maintainer at [email protected] or @hoxworth for faster resolution.
 
 Releases follow semantic versioning and may be made at a maintainer's discretion.