Replace Boost usage with C++11 features

- Adds 'std=c++11' compiler flags
 - Replaces boost::type_traits with std::type_traits
 - Replaces boost::shared_ptr with std::shared_ptr
 - Replaces std::auto_ptr with std::unique_ptr
 - Replaces raw pointers with std::unique_ptr in ptr_vector, ptr_stack, and SettingChanges
 - Replaces boost::noncopyable with deleted copy and assignment operators
 - Replaces boost::next with std::next
 - Replaces boost::enable_if with std::enable_if
 - Replaces boost::is_convertible with std::is_convertible
 - Replaces ptrdiff_t with std::ptrdiff_t
 - Replaces boost::iterator_facade and boost::iterator_adaptor with std::iterator, borrowing the 'proxy reference' technique from boost
 - Removes Boost dependency from CMakeLists
 - Formats changed files using clang-format

src/singledocparser.h

@@ -53,7 +53,7 @@ class SingleDocParser : private noncopyable {
  private:
   Scanner& m_scanner;
   const Directives& m_directives;
-  std::auto_ptr<CollectionStack> m_pCollectionStack;
+  std::unique_ptr<CollectionStack> m_pCollectionStack;
 
   typedef std::map<std::string, anchor_t> Anchors;
   Anchors m_anchors;