Resolve extends and include arguments as variables

Stencil/TemplateLoader/Include.swift

@@ -2,19 +2,19 @@ import PathKit
 
 
 public class IncludeNode : NodeType {
-  public let templateName: String
+  public let templateName: Variable
 
   public class func parse(parser: TokenParser, token: Token) throws -> NodeType {
-    let bits = token.contents.characters.split("\"", allowEmptySlices: true).map(String.init)
+    let bits = token.components()
 
-    guard bits.count == 3 else {
+    guard bits.count == 2 else {
       throw TemplateSyntaxError("'include' tag takes one argument, the template file to be included")
     }
 
-    return IncludeNode(templateName: bits[1])
+    return IncludeNode(templateName: Variable(bits[1]))
   }
 
-  public init(templateName: String) {
+  public init(templateName: Variable) {
     self.templateName = templateName
   }
 
@@ -23,6 +23,10 @@ public class IncludeNode : NodeType {
       throw TemplateSyntaxError("Template loader not in context")
     }
 
+    guard let templateName = try self.templateName.resolve(context) as? String else {
+      throw TemplateSyntaxError("'\(self.templateName)' could not be resolved as a string")
+    }
+
     guard let template = loader.loadTemplate(templateName) else {
       let paths = loader.paths.map { $0.description }.joinWithSeparator(", ")
       throw TemplateSyntaxError("'\(templateName)' template not found in \(paths)")