Apply formatting/style tweaks to comply with compile time diagnostics for g++ and clang++ (#686)

* Add compilation flags: -Wshadow -Weffc++ -pedantic -pedantic-errors
* Delete implicit copy & move constructors & assignment operators
  in classes with pointer data members.
* An exception to the above: Add default copy & move constructors &
  assignment operators for the Binary class.
* Convert boolean RegEx operators to binary operators.
* Initialize all members in all classes in ctors.
* Let default ctor delegate to the converting ctor in
  Binary and RegEx
* Don't change any tests except regex_test (as a result of the change
  to binary operators).

Note: https://bugzilla.redhat.com/show_bug.cgi?id=1544675 makes
-Weffc++ report a false positive in "include/yaml-cpp/node/impl.h".

src/ostream_wrapper.cpp

@@ -14,7 +14,12 @@ ostream_wrapper::ostream_wrapper()
       m_comment(false) {}
 
 ostream_wrapper::ostream_wrapper(std::ostream& stream)
-    : m_pStream(&stream), m_pos(0), m_row(0), m_col(0), m_comment(false) {}
+    : m_buffer{},
+      m_pStream(&stream),
+      m_pos(0),
+      m_row(0),
+      m_col(0),
+      m_comment(false) {}
 
 ostream_wrapper::~ostream_wrapper() {}
 
@@ -54,4 +59,4 @@ void ostream_wrapper::update_pos(char ch) {
     m_comment = false;
   }
 }
-}
+}  // namespace YAML