Allow template filters to throw errors

StencilSpecs/VariableSpec.swift

@@ -20,49 +20,49 @@ describe("Variable") {
 
   $0.it("can resolve a string literal with double quotes") {
     let variable = Variable("\"name\"")
-    let result = variable.resolve(context) as? String
+    let result = try variable.resolve(context) as? String
     try expect(result) == "name"
   }
 
   $0.it("can resolve a string literal with single quotes") {
     let variable = Variable("'name'")
-    let result = variable.resolve(context) as? String
+    let result = try variable.resolve(context) as? String
     try expect(result) == "name"
   }
 
   $0.it("can resolve a string variable") {
     let variable = Variable("name")
-    let result = variable.resolve(context) as? String
+    let result = try variable.resolve(context) as? String
     try expect(result) == "Kyle"
   }
 
   $0.it("can resolve an item from a dictionary") {
     let variable = Variable("profiles.github")
-    let result = variable.resolve(context) as? String
+    let result = try variable.resolve(context) as? String
     try expect(result) == "kylef"
   }
 
   $0.it("can resolve an item from an array via it's index") {
     let variable = Variable("contacts.0")
-    let result = variable.resolve(context) as? String
+    let result = try variable.resolve(context) as? String
     try expect(result) == "Katie"
   }
 
   $0.it("can resolve the first item from an array") {
     let variable = Variable("contacts.first")
-    let result = variable.resolve(context) as? String
+    let result = try variable.resolve(context) as? String
     try expect(result) == "Katie"
   }
 
   $0.it("can resolve the last item from an array") {
     let variable = Variable("contacts.last")
-    let result = variable.resolve(context) as? String
+    let result = try variable.resolve(context) as? String
     try expect(result) == "Carlton"
   }
 
   $0.it("can resolve a value via KVO") {
     let variable = Variable("object.title")
-    let result = variable.resolve(context) as? String
+    let result = try variable.resolve(context) as? String
     try expect(result) == "Hello World"
   }
 }