(#29) Add missing release notes to generated packages

[AdmiringWorm]

Description Of Changes

This adds a version substitution to the nuspec file to automatically insert the version to the release notes link when a package is generated.

Motivation and Context

We want to have a link to the release notes when we push a package to the Chocolatey Community Repository.

Testing

1. Run .\build.ps1.
2. Navigate to code_drop\Packages\Chocolatey.
3. Extract the nupkg file.
4. Open up the nuspec file.
5. Ensure that the release notes element have the version number specified in the URL.

Operating Systems Testing

• Windows 10

Change Types Made

• [ ] Bug fix (non-breaking change).
• [x] Feature / Enhancement (non-breaking change).
• [ ] Breaking change (fix or feature that could cause existing functionality to change).
• [ ] Documentation changes.
• [ ] PowerShell code changes.

Change Checklist

• [ ] Requires a change to the documentation.
• [ ] Documentation has been updated.
• [ ] Tests to cover my changes, have been added.
• [ ] All new and existing tests passed?
• [ ] PowerShell code changes: PowerShell v2 compatibility checked?

Related Issue

Fixes #29