fix(context): Allow removing a value at a pushed state

Sources/Context.swift

@@ -1,6 +1,6 @@
 /// A container for template variables.
 public class Context {
-  var dictionaries: [[String: Any]]
+  var dictionaries: [[String: Any?]]
   let namespace: Namespace
 
   /// Initialise a Context with an optional dictionary and optional namespace
@@ -58,9 +58,11 @@ public class Context {
 
     for dictionary in dictionaries {
       for (key, value) in dictionary {
+        if let value = value {
           accumulator.updateValue(value, forKey: key)
         }
       }
+    }
 
     return accumulator
   }

Tests/StencilTests/ContextSpec.swift

@@ -47,6 +47,15 @@ func testContext() {
       try expect(context["name"] as? String) == "Kyle"
     }
 
+    $0.it("allows you to remove a parent's value in a level") {
+      try context.push {
+        context["name"] = nil
+        try expect(context["name"]).to.beNil()
+      }
+
+      try expect(context["name"] as? String) == "Kyle"
+    }
+
     $0.it("allows you to push a dictionary and run a closure then restoring previous state") {
       var didRun = false