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/scanner.cpp

@@ -233,8 +233,8 @@ const RegEx& Scanner::GetValueRegex() const {
 void Scanner::StartStream() {
   m_startedStream = true;
   m_simpleKeyAllowed = true;
-  std::auto_ptr<IndentMarker> pIndent(new IndentMarker(-1, IndentMarker::NONE));
-  m_indentRefs.push_back(pIndent);
+  std::unique_ptr<IndentMarker> pIndent(new IndentMarker(-1, IndentMarker::NONE));
+  m_indentRefs.push_back(std::move(pIndent));
   m_indents.push(&m_indentRefs.back());
 }
 
@@ -281,7 +281,7 @@ Scanner::IndentMarker* Scanner::PushIndentTo(int column,
   if (InFlowContext())
     return 0;
 
-  std::auto_ptr<IndentMarker> pIndent(new IndentMarker(column, type));
+  std::unique_ptr<IndentMarker> pIndent(new IndentMarker(column, type));
   IndentMarker& indent = *pIndent;
   const IndentMarker& lastIndent = *m_indents.top();
 
@@ -298,7 +298,7 @@ Scanner::IndentMarker* Scanner::PushIndentTo(int column,
 
   // and then the indent
   m_indents.push(&indent);
-  m_indentRefs.push_back(pIndent);
+  m_indentRefs.push_back(std::move(pIndent));
   return &m_indentRefs.back();
 }