Frosting 0.38.4 Release

Useful information

[x] Make sure all issues within the milestone are tagged with either Bug, Feature, Improvement, Documentation, Breaking change, or Build
[x] Make sure all issues associated with the milestone are closed
[x] Make sure that all issues only have 1 label associated with them

[x] Create branch locally to match the name of the release, for example git checkout -b release/0.35.0 develop
[x] Create release notes on GitHub using the ReleaseNotes task (.\build.ps1 --target=CreateReleaseNotes)
[x] Build everything (./build.ps1) to make sure it works.
[x] At this point, if you want to share the work to date, and validate something, push the local release branch to GitHub
[x] Assuming everything is ok, switch to master branch (git checkout master)
[x] Merge release branch to the master git merge --no-ff release/0.35.0
[x] Build everything (./build.ps1) to make sure it works (we can never be too sure).
[x] Push master branch.
[x] Make sure that the AppVeyor build succeeds before going any further.
[x] Assuming that everything went ok, go to the draft release in GitHub and click Edit
[x] Click the Publish Release button
[x] This will trigger another build in AppVeyor, but this time with a tag.
[x] Switch to develop branch git checkout develop
[x] Merge release branch into develop git merge --no-ff release/0.35.0
[x] Resolve any merge conflicts
[x] Build everything (./build.ps1) to make sure it works.
[x] Push develop branch.
[x] Delete the local release branch that was created git branch -d release/0.35.0 (and the remote one, if pushed to GitHub git push origin --delete release/0.35.0)

[x] Make sure that everything has pushed correctly to nuget
- Cake.Frosting
- Cake.Frosting.Template
[x] Go and have a drink!