Exposed components begin/end

Allows iteration over a components children.
Updated Remove function to conform to vector::erase

include/ftxui/component/component_base.hpp

@@ -29,10 +29,14 @@ class ComponentBase {
   // ComponentBase hierarchy.
   ComponentBase* Parent();
   void Add(Component children);
-  void Remove(std::size_t idx);
+  void Remove(Components::iterator child);
   // Renders the component.
   virtual Element Render();
 
+  // Iterate over component children
+  Components::iterator begin();
+  Components::iterator end();
+
   // Handles an event.
   // By default, reduce on children with a lazy OR.
   //

src/ftxui/component/component.cpp

@@ -44,10 +44,24 @@ void ComponentBase::Add(Component child) {
 /// @brief Remove a child.
 /// @@param idx The child index to be removed.
 /// @ingroup component
-void ComponentBase::Remove(std::size_t idx) {
-  children_.erase(children_.begin()+idx);
+void ComponentBase::Remove(Components::iterator child) {
+  children_.erase(child);
 }
 
+/// @brief Obtain an iterator to the first child
+/// @ingroup component
+Components::iterator ComponentBase::begin() {
+  return children_.begin();
+}
+
+/// @brief Obtain an iterator to one after the last child
+/// @ingroup component
+Components::iterator ComponentBase::end() {
+  return children_.end();
+}
+
+
+
 /// @brief Draw the component.
 /// Build a ftxui::Element to be drawn on the ftxi::Screen representing this
 /// ftxui::ComponentBase.