FSM_INITIAL_STATE Macro only works in global namespace

I observed that the macro `FSM_INITIAL_STATE` doesn't compile if invoked outside of the global namespace. The examples I looked at all use the global namespace so it isn't clear to me if much though was given to namespaces by the author.

example code that wont compile:
```
#include

namespace xxx::yyy {

// ----------------------------------------------------------------------------
// 1. Event Declarations
//

struct AAA : tinyfsm::Event { };
struct BBB : tinyfsm::Event { };

// ----------------------------------------------------------------------------
// 2. State Machine Base Class Declaration
//
struct SM : tinyfsm::MealyMachine
{
virtual void react(AAA const &) { };
virtual void react(BBB const &) { };
};

// ----------------------------------------------------------------------------
// 3. State Declarations
//

struct Wait : SM
{};

struct Off : SM
{};

FSM_INITIAL_STATE(SM, Off)

} // namespace xxx::yyy
```

Solution is to use the macro in the global namespace and fully qualify the state machine and state types:

```
#include

namespace xxx::yyy {

// ----------------------------------------------------------------------------
// 1. Event Declarations
//

struct AAA : tinyfsm::Event { };
struct BBB : tinyfsm::Event { };

// ----------------------------------------------------------------------------
// 2. State Machine Base Class Declaration
//
struct SM : tinyfsm::MealyMachine
{
virtual void react(AAA const &) { };
virtual void react(BBB const &) { };
};

// ----------------------------------------------------------------------------
// 3. State Declarations
//

struct Wait : SM
{

};

struct Off : SM
{

};
} // namespace xxx::yyy

FSM_INITIAL_STATE(xxx::yyy::SM, xxx::yyy::Off)
```

Is it possible to rework FSM_INITIAL_STATE to allow invocation within a custom namespace?