Updated release notes

Removed redundant pull request commit lookups, optimised unreleased c…

…ommits search and updated nuspec to comply with Chocolatey requirements

Added support for Slack post publishing and refactored markdown forma…

…tter so that notes are staged in Semantic Release Notes object first and renamed to PullRequestReleaseNotes

Merge pull request jasminsehic#5 from jasminsehic/InjectGitVersion

Added ability to inject a release version number from GitVersion

Merge pull request jasminsehic#4 from jasminsehic/ExcludeLabelFeature

Added ExcludeLabel parameter to README.md

Added note about GitHubToken environment variable option

Initial commit