Add architecture document and docs

Stencil/Template.swift

@@ -1,12 +1,15 @@
 import Foundation
 
+/// A class representing a template
 public class Template {
     public let parser:TokenParser
 
+    /// Create a template with the given name inside the main bundle
     public convenience init?(named:String) {
         self.init(named:named, inBundle:nil)
     }
 
+    /// Create a template with the given name inside the given bundle
     public convenience init?(named:String, inBundle bundle:NSBundle?) {
         var url:NSURL?
 
@@ -19,6 +22,7 @@ public class Template {
         self.init(URL:url!)
     }
 
+    /// Create a template with a file found at the given URL
     public convenience init?(URL:NSURL) {
         var error:NSError?
         let maybeTemplateString = NSString(contentsOfURL: URL, encoding: NSUTF8StringEncoding, error: &error)
@@ -30,12 +34,14 @@ public class Template {
         }
     }
 
+    /// Create a template with a template string
     public init(templateString:String) {
         let lexer = Lexer(templateString: templateString)
         let tokens = lexer.tokenize()
         parser = TokenParser(tokens: tokens)
     }
 
+    /// Render the given template in a context
     public func render(context:Context) -> Result {
         switch parser.parse() {
             case .Success(let nodes):
@@ -46,6 +52,7 @@ public class Template {
         }
     }
 
+    /// Render the given template without a context
     public func render() -> Result {
         let context = Context()
         return render(context)