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/directives.cpp

@@ -1,12 +1,7 @@
 #include "directives.h"
 
 namespace YAML {
-Directives::Directives() {
-  // version
-  version.isDefault = true;
-  version.major = 1;
-  version.minor = 2;
-}
+Directives::Directives() : version{true, 1, 2}, tags{} {}
 
 const std::string Directives::TranslateTagHandle(
     const std::string& handle) const {
@@ -19,4 +14,4 @@ const std::string Directives::TranslateTagHandle(
 
   return it->second;
 }
-}
+}  // namespace YAML