Support rendering URLs

This patch was authored and released by @tanner0101.

Adds support for serializing URLs in templates (#38, fixes #64).

TemplateKit 1.4.0

New:

• Adds a new init method DateFormat(defaultDateFormatterFactory: () -> DateFormatter) (#45)
• Adds a new static DateFormat.iso8601 tag that uses ISO-8601 formatting (#45)

TemplateKit 1.3.0

New:

• Performance improvements to HTML string escaping (#56)
• New String.htmlEscaped() method (#56)

TemplateKit 1.2.0

New:

• TemplateDataEncoder has been refactored for improved performance. (#50)
• DateFormatters are now cached during rendering for improved performance. (#51)

Fixed:

• DateFormat now returns null when arguments are null. (#44)
• Context userInfo does now get passed to nested scopes. (#53, #54)
• Using #for on null array now returns null. (#55)

TemplateKit 1.1.2

Fixed:

• Fixed an issue with UnsafeBufferPointer in Swift 5. (#46)

TemplateKit 1.1.1

Fixed:

• userInfo is now correctly passed when using #embed. (#41, #42)

TemplateKit 1.1.0

New:

• Performance improvements for files loaded from disk. (#24)
• ViewRenderer now supports passing a userInfo dictionary that will be accessible by TagRenderers. (#17, #28)

return req.view().render("welcome", ["name": "Vapor"], userInfo: ["foo": "bar"])

final class FooTag: TagRenderer {
    func render(_ tag: TagContext) -> ... { 
        print(tag.context.userInfo["foo"])
    }
}

Fixed:

• Fixed issue which could cause incorrect views to be returned from cache. (#26, #25, #31).
• Fixed LeafDataEncoder to properly recognize custom encoding methods. (#29, #20, #30).
• Fixed #date tag crasher. (#23)

TemplateKit 1.0.1

Fixed:

• Re-added ViewRenderer.

Milestone:
1.0.1

TemplateKit 1.0.0

Introducing Template Kit 1.0 🎉
Template Kit is an easy-to-use foundation for building powerful templating languages in Swift.

Docs:
https://docs.vapor.codes/3.0/template-kit/getting-started/

API Docs:
https://api.vapor.codes/template-kit/latest/TemplateKit

Milestone:
1.0.0

---

Changes since final release candidate:

Fixed:

• Audited and internalized several APIs to minimize API surface.
• Removed TemplateData.future case in favor of TagRenderers returning Future<TemplateData> (was redundant previously).
• Added lots of missing doc blocks, now at 100% docs coverage.

Template Kit 1.0.0 RC 2.0.1

New:

• Adds isFirst and isLast variables alongside index while using iterators.