[C++11] std::move / std::forward

Quoted from Effective Modern C++:

• Neither std::move nor std::forward do anything at runtime.
• Apply std::move to rvalue references and std::forward to universal references the last time each is used.
• Do the same thing for rvalue references and universal references being returned from functions that return by value.
• Never apply std::move or std::forward to local objects (including by-value parameters) if they would otherwise be eligible for the return value optimization.
• Overloading on universal references almost always leads to the universal reference overload being called more frequently than expected.
• Perfect-forwarding constructors are especially problematic, because they’re typically better matches than copy constructors for non-const lvalues, and they can hijack derived class calls to base class copy and move constructors.
• Alternatives to the combination of universal references and overloading include the use of distinct function names, passing parameters by (lvalue)-reference-to-const, passing parameters by value, and using tag dispatch.
• Universal reference parameters often have efficiency advantages, but they also have usability disadvantages.
• Reference collapsing occurs in four contexts: 
• template instantiation, 
• auto type generation, 
• creation and use of typedefs and alias declarations,
• decltype.