Error in test_stats

[mgcooper]

When compiling, I got an error on the tests:

[ 89%] Building CXX object test/CMakeFiles/catch_tests.dir/test_stats.cpp.o
/Users/coop558/myprojects/exactextract/test/test_stats.cpp:117:23: error: implicit instantiation of undefined template 'std::basic_stringstream<char>'
    std::stringstream ss;
                      ^
/Library/Developer/CommandLineTools/SDKs/MacOSX14.4.sdk/usr/include/c++/v1/__fwd/sstream.h:29:28: note: template is declared here
class _LIBCPP_TEMPLATE_VIS basic_stringstream;
                           ^
1 error generated.
make[2]: *** [test/CMakeFiles/catch_tests.dir/test_stats.cpp.o] Error 1
make[1]: *** [test/CMakeFiles/catch_tests.dir/all] Error 2
make: *** [all] Error 2

The fix is just to add #include <sstream>

[dbaston]

Added in 0e13cb4