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/emitfromevents.cpp

@@ -16,10 +16,11 @@ std::string ToString(YAML::anchor_t anchor) {
   stream << anchor;
   return stream.str();
 }
-}
+}  // namespace
 
 namespace YAML {
-EmitFromEvents::EmitFromEvents(Emitter& emitter) : m_emitter(emitter) {}
+EmitFromEvents::EmitFromEvents(Emitter& emitter)
+    : m_emitter(emitter), m_stateStack{} {}
 
 void EmitFromEvents::OnDocumentStart(const Mark&) {}
 
@@ -116,4 +117,4 @@ void EmitFromEvents::EmitProps(const std::string& tag, anchor_t anchor) {
   if (anchor)
     m_emitter << Anchor(ToString(anchor));
 }
-}
+}  // namespace YAML