Copy configs

Add a config file and copy it to build directory after build succeeded.

Closes #4 (closed)

exple-cmake-build/exple-expr.hpp

 #include "exple-add.h"
 #include "exple-mul.h"
+#include "exple-substract.h"
 
 namespace exple
 {
   int add_and_mul( int a, int b, int c);
+    int add_and_sub( int a, int b, int c);
+
 }
 
 int exple::add_and_mul( int a, int b, int c)
 {
   return exple::mul(exple::add(a, b), c);
 }
+
+int exple::add_and_sub( int a, int b, int c)
+{
+    return exple::mul(exple::substract(a, b), c);
+}