Fixed problems in testing addition operations

More carefully defined the concepts.  That is the concept of the library is now clear:

Trap at either compile or runtime integer operations which yield a result which differs from the normal arithmetic result.

Pending on this check in:
a) only addition is fixed up so far
b) uses BOOST_TYPEOF... rather than decltype(... - final decision sill pending.
c) comments out some compile time checks which should be re-instated.
d) fixed tests so that they actually work!

test/test.cpp

@@ -8,6 +8,7 @@
 #include <cstdlib>   // EXIT_SUCCESS
 
 #include <boost/mpl/print.hpp>
+
 #include "../include/safe_range.hpp"
 #include "../include/safe_integer.hpp"
 
@@ -36,7 +37,6 @@ bool test1(){
             int
         >::type
     >::type t3;
-
     zi = x + yi;
     
     bool success = false;