Add an include tag

Stencil/Parser.swift

@@ -36,6 +36,7 @@ public class TokenParser {
         registerTag("if", IfNode.parse)
         registerTag("ifnot", IfNode.parse_ifnot)
         registerTag("now", NowNode.parse)
+        registerTag("include", IncludeNode.parse)
     }
 
     /// Registers a new template tag

Stencil/TemplateLoader.swift

@@ -11,7 +11,7 @@ import PathKit
 
 // A class for loading a template from disk
 public class TemplateLoader {
-    let paths:[Path]
+    public let paths:[Path]
 
     public init(paths:[Path]) {
         self.paths = paths

Stencil/TemplateLoader/Include.swift

@@ -0,0 +1,44 @@
+import Foundation
+import PathKit
+
+extension String : Error {
+    public var description:String {
+        return self
+    }
+}
+
+public class IncludeNode : Node {
+    public let templateName:String
+
+    public class func parse(parser:TokenParser, token:Token) -> TokenParser.Result {
+        let bits = token.contents.componentsSeparatedByString("\"")
+
+        if bits.count != 3 {
+            return .Error(error:NodeError(token: token, message: "Tag takes one argument, the template file to be included"))
+        }
+
+        return .Success(node:IncludeNode(templateName: bits[1]))
+    }
+
+    public init(templateName:String) {
+        self.templateName = templateName
+    }
+
+    public func render(context: Context) -> Result {
+        if let loader =  context["loader"] as? TemplateLoader {
+            if let template = loader.loadTemplate(templateName) {
+                return template.render(context)
+            }
+
+            let paths:String = join(", ", loader.paths.map { path in
+                return path.description
+            })
+            let error = "Template '\(templateName)' not found in \(paths)"
+            return .Error(error)
+        }
+
+        let error = "Template loader not in context"
+        return .Error(error)
+    }
+}
+