cql/internal/cql_promise.hpp: No such file or directory

Since merging dev branch into master, the file "cql_connection.hpp" includes "cql/internal/cql_promise.hpp". "make install" does not copy the "internal" directory to "/usr/include/cql". So, it is not possible to use the include file "cql_connection.hpp" from "/usr/include/cql".
 
```
In file included from CassandraAdapter.cpp:55:0:
/usr/include/cql/cql_connection.hpp:41:40: fatal error: cql/internal/cql_promise.hpp: No such file or directory
compilation terminated.
make[2]: *** [CassandraAdapter.o] Error 1
```