C++ - better => butter

Summary:
Renaming the `better` utilities to `butter`:
- to prevent claims that this library is superior to others - it really depends on use cases
- to indicate ease of use throughout the codebase, easily spread like butter

Changelog: [C++][Changed] Renaming C++ better util to butter, used by Fabric internals

Reviewed By: JoshuaGross

Differential Revision: D33242764

fbshipit-source-id: 26dc95d9597c61ce8e66708e44ed545e0fc5cff5

ReactCommon/react/renderer/debug/debugStringConvertibleUtils.h

@@ -7,7 +7,7 @@
 
 #pragma once
 
-#include <better/optional.h>
+#include <butter/optional.h>
 #include <limits>
 #include <memory>
 #include <string>
@@ -34,7 +34,7 @@ debugStringConvertibleItem(std::string name, T value, T defaultValue = {}) {
 template <typename T>
 inline SharedDebugStringConvertible debugStringConvertibleItem(
     std::string name,
-    better::optional<T> value,
+    butter::optional<T> value,
     T defaultValue = {}) {
   if (!value.hasValue()) {
     return nullptr;